The Army’s computers have been hacked, and their data is being erased from the screen. The Supply Sergeant, who is in charge of outfitting an incoming platoon of 250 recruits that day, starts to panic about the loss of data.
Just before their inventory disappears, a smart clerk finds and scribbles down that they have 1126 individual items sitting in the storeroom from the shipments they just received. This clerk also knows that the army berets came in stacks of 140, rifles in piles of 105, uniforms in crates of 84, and boots in boxes of 60 pairs.
The Supply Sergeant doesn't know if he will be able to outfit the entire company of 250 recruits, so that each recruit gets a beret, a rifle, a uniform, and a pair of boots. The clerk thinks he can deduce it. Are the supplies in the storeroom sufficient, or will they need more?
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
great explanation!
Using this same technique what you could have also done was that after removing thee 336 uniforms u remove 280 berets (assume there are 2 stacks as we need tht many ) and the remainder 1126-280-336 will come upto 510. There is only one possible way to split 510 into two numbers x and y such that x mod 105 and y mod 60 is zero (which becomes very evident just by looking at 510) therefore deducing that there have to be 210 rifles and that the rifles arent enough...
thank you for the excellent deduction....
I did the same :D
Let x , y , z , w be the number of units of berets, rifles, uniforms, and boots, respectively. We get 1 4 0 x + 1 0 5 y + 8 4 z + 6 0 w = 1 1 2 6 . Looking mod 3 , 5 , 7 , we get x ≡ 2 mod 3 , z ≡ 4 mod 5 , w ≡ 5 mod 7 . Writing x = 2 + 3 x 0 , z = 4 + 5 z 0 , w = 5 + 7 w 0 , we get 4 2 0 x 0 + 1 0 5 y + 4 2 0 z 0 + 4 2 0 w 0 = 2 1 0 . Since all the variables are nonnegative integers, it's clear by inspection that the only solution is y = 2 and all the others are 0 .
So there is a unique solution ( x , y , z , w ) = ( 2 , 2 , 4 , 5 ) in nonnegative integers. There are 280 berets, 210 rifles, 336 uniforms, and 300 pairs of boots. That's not enough rifles.
can you please explain how you arrived at x,y,z being 2mod3, 4mod5, 5mod7?
Log in to reply
Let's pick one: if we reduce both sides of the equation mod 7, we get 6 0 w ≡ 1 1 2 6 mod 7 , which reduces to 4 w ≡ 6 . The multiplicative inverse of 4 mod 7 is 2 , so w ≡ 6 ⋅ 2 ≡ 5 . The other two are similar.
The point is that reducing mod 3 , 5 , or 7 is convenient because it eliminates all but one of the terms on the left side.
please show more steps so that a layman can understand
What method are you using sir? How did you get all that mod?? Pls elaborate..
i did a cal mistake
i cant clear understnd
Hi Patrick. Excellent use of the modulo operation. I have not used this in a while and am a little confused about one and only one thing. I get it why we use 2mod3 and 5mod7.
But why have we used 4mod5? Why could not we not use 3mod5 or 2mod5 for z? Is it because 4mod5 leaves a multiple of 105 on the RHS? Thanks again for the excellent solution. Cheers
Okay guys this is how I cracked it
Since we are given a total number of 1126 individual items, first we find the total number of berets , rifles , uniforms and boots that make up this total: that is we find the number of stacks that each contain 140 berets , the number of piles that each contain 105 rifles , the number of crates that each contain 84 uniforms and the number of boxes that each contain 60 pairs of boots .
Is almost a tedious process to figure out the exact number of stacks, piles, crates and boxes of berets, rifles, uniforms and boots respectively but on closer examination, we can do this;
The only single digit numbers that gives a unit digit of 6 when they multiply 4 are 9 and 4. Thus the possible number of crates of uniforms are 4 or 9. On doing trial and error, 9 is too big so the only possible number of crates of uniforms each containing 84 uniforms are 4.
2 in this case is the smallest possible number that can multiply 5 and gives a unit digit of 0. Thus the possible number of piles of rifles each containing 105 guns are 2.
This leaves us with the berets and boots.
Adding the total number of rifles and uniforms gives 546 and taking this sum from the total number of individual items we are left with 580 individual items.
Clearly, to get a sum of 580 between the berets and the boots, we simply multiply the number of berets in each stack by 2 and the number of pairs of boots in each box by 5. Thus we have;
The number of berets in each stack equals 2 × 1 4 0 = 2 8 0
The number of rifles in each pile equals 2 × 1 0 5 = 2 1 0
The number of uniforms in each crate equals 4 × 8 4 = 3 3 6
The number of pairs of boots in each box equals 5 × 6 0 = 3 0 0
These sums add up to 1126 individual items .
Clearly there are less rifles to outfit all the 250 recruits .
Hence the correct answer is * No, they do not have enough rifles * .
If the stacks come in packs of the given no of items, the question should be specified whether it was completely packed and not partial one. Coz I considered the case if any stack contain incomplete no of items as it was given that it contains individual no of items.
First let the number of berets be = a , number of rifles be = b, number of uniform be = c and number of boots =d.
Now as per given in the question, we get an eqn : 140a + 105b + 84c + 60d = 1126
here, the mod represents : a= 2mod3 d= 5mod7 c= 4mod5 ( put a= 2+3x' ; c=4+5c' ; d=5+7d')
Final Eqn: 420a' + 105b + 420c' + 420d' = 210
If we put b=2, all others will become zero.
[a,b,c,d] = [2,2,4,5]
-> Results : 336 uniforms, 300 boots, 210 rifles & 280 berets.
-> Therefore, there are not many rifles !
LOL ! Hahaha Patrick we did the same man ! :p Hahaa I recently saw that you even solved by the same method !
Pls can you explain what way are you solving it?? What method are you using ? Where did all that come from?
plz tell me is that mod method in class 12th :(
they have 336 uniforms(84 X 4) , 300 boots(60 X 5) , 280 berets(140 X 2) , and 210 refiles (105 X 2) , which totals 1126 individual items. Therefore they have 40 refiles less.
I did this by writing a table of multiples of 140, 105, 84 and 60 (corresponding to berets, refiles, uniforms and boots respectively). Since the total of items is exactly 1126, multiples of these four numbers must add up to 1126. We immediately know that there cannot be an odd number piles of rifles, since 105 is odd (the unit digit would be odd and never 6 of 1126). Therefore there must be either 2 or 4 piles of rifles. If there were 4 piles, there would be 1 0 5 × 4 = 4 2 0 , which doesn't leave much for the other items, and there is no possible combination to make 1126. So there must be 2 piles of rifles. Since the entire company has 250 recruits, and 1 0 5 × 2 = 2 1 0 ; the answer is "No, they do not have enough rifles."
If all items are sufficient for the whole company, there would be:
In that case,
Number of items = (140x2) + (105x3) + (84x3) + (60x5) = 1147 items
This exceeds the total number of items available by (1147-1126) = 21 units.
Looking through the figures, we find that if we increase the number of uniform crates by 1 and reduce the number of rifle piles by 1, the total number of items will be reduced by 21 units.
Checking:
Number of items = (140x2) + (105x2) + (84x4) + (60x5) = 1126 items
Therefore the answer is "they don't have enough uniform".
Sorry, I mean "they don't have enough rifles". Should've done the proofread at least twice.
Don't get bewildered by a wordy problem; apply simple Maths.
As each of 250 recruits is to be provided with a beret, a rifle, a uniform, and a pair of boots, minimum No. of Individual Items (denoted by II hereafter) needed is 1000.
Now, notice the last digit of 1126 ( 6 ). We can deduce that No. of Uniform-Crates is 4 so that we land up having 6 at Unit's place.
We could have chosen 9 Uniform-Crates even, but the problem is the II . 9 Uniform-Crates → 756 uniforms ⇒ ( 1126 - 756 = 370 left II ). And Certainly, we can't see the recruits without rifles or even boots! Can we? (Minimum II needed is 750, condition met by 4 Uniform-Crates ONLY)
Now, we are left with (1126 - (4 × 84)) = 790 II
With 790 II we can't distribute the supplies to 280 (needing 840) and 300 (needing 900) recruits. So, Option 2 and Option 4 can be eliminated. Option 1 stands incorrectly as we've already successfully distributed the uniforms. So, Option 3 is the correct answer because no. of rifles is insufficient.
we should have 2 stacks of berets, 2 piles of rifles, 4 crates of uniforms and 5 boxes of shoes. to get the total number of items as 1126. thus there are 280 berets, 210 rifles, 336 uniforms and 300 pairs of boots and hence they donot have enough rifles.
We have sets of berets (call them BER: 1 BER = 140), rifles (RIF), uniforms (UNI) and boots (BOT). The total number is 1126 i.e. w * BER + x * RIF + y * UNI + z * BOT = 1126. Here, BER = 140, RIF = 105, UNI = 84, BOT = 60.
We need to start eliminating the variables w, x, y, z etc. We'll use modulo arithmetic for this. As you can see, RIF, UNI and BOT are divisible by 3 but BER is not. If you divide BER by 3 you get 2 as a remainder.
w * BER mod 3 + x * RIF mod 3 + ... = 1126 mod 3 (divide both sides by 3 and calculate the remainders)
=> (w * 2) mod 3 = 1 (RIF, UNI and BOT all have 0 after we take modulo 3)
=> w = 2, 5, 8... 8 is impossible since then all the items except 6 will become berets! (And the minimum stack size is 60, for boots.) Only possibilities are then w = 2, 5.
First, we can check if we get a fit solution for x, y, z with w = 2. We can eliminate x by mod 6 and then y by mod 10.
One possible solution then becomes: 2 BER, 2 RIF, 4 UNI, 5 BOT. There may be other solutions but we've already found one possible case where there are not enough items; in this case there are only 2 * 105 = 210 rifles.
So we know which answer to pick!
no, is confirm so you start thinking for only two option....you will easily get answer
To solve this problem,u should first see the total number of individual items available. i.e. 1126 since the unit's place has 6 in individual items and 0,5,4 and 0 in case of stacks of beret,rifle,uniform and boots Now let us try to reduce the individual number of items,for that 1126 has 6 in units place so considering uniforms it has to be a multiple of 4 or 7 stacks.4 is the best choice,which leaves 1126-376 items. Now we have 750 items.Lets try to reduce this number again..So we take an account of boots for minimum of 250,we must multiply number of boot stacks by 5,which leaves 750-300=450 individual items So the equation now becomes 140x+105y=450. To satisfy 280 of them,x must be multiple of 2,which leaves insufficient number of rifles .
I just did the minimum required numbers of each boxes required for an army of 250.... The minimum number of army berets are 2 forming 280 items, rifles required are 3 forming 315 items, uniforms are 3 forming 252 items and boots are 5 forming 300 pairs. Now all these add up to 1147 causing an excess of 21 items. As 105-84 = 21, therefore in the shipment, one less box of rifles is present and one more box of uniforms are present.... Its an indirect method....
84 x 4 = 336, not 376
Problem Loading...
Note Loading...
Set Loading...
As the total number of items is an even number, and all the items come in piles of even numbers except for rifles, you know that there is an even number of piles of rifles (minimum number 210).
Also, as the total number is 1126, you know that the number of uniforms must end in 6 (Minimum of 336 uniforms), since all the other items (rifles included) come in multiples of ten.
So the minimum number of rifles is 210, minimum number of uniforms 336, minimum number of berets 140, and minimum number of pairs of boots 60. (Total 746)
As there aren't enough rifles in this situation, consider that there are 420 instead. This would mean a total of 956 iteams, with 170 still to go. However as no comination of 84, 140 and 60 adds up to 170, there cannot be 420 rifles. Instead consider there are 630 rifles, this would mean the total is 1166 items, which is too many. Therefore there cannot be more than 210 rifles, which is not enough.