I have 3 distinct positive integers.
The sum of these three integers is either 5, 6 or 7.
The product of these three integers is either 8, 9 or 10.
What is the median of these three integers?
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.
Good clear explanation!
While it is true the product must be 8, this is not even necessary to consider. The problem can be solved from the first condition only, because the median is 2 whether the sum is 6 or 7.
"The only way to write seven as a sum of three distinct positive integers is product = 8." Wait you say "to write seven" then you equal it to 8? ("=> product =8") Is this a typo or I just didn't get it?
Log in to reply
Sorry if I was not clear. 7 = 1 + 2 + 4. The product of 1, 2, and 4 is 8.
I do not get it. 1+2+4=7 but 1+2+4 does not equal 8
Log in to reply
The sum is 1 + 2 + 4 = 7 , and the product 1 × 2 × 4 is 8.
Sum is 7 = 1 + 2 + 4. (i.e. Sum => add the numbers together) Product is 8 = 1 * 2 * 4. (i.e. Product => multiple the numbers together)
For it to be a product of one of those three integers, you must look at its factors. Decomposing each into its primes:
8 = 4x2x1 = 2x2x2x1,
9 = 3x3x1, and
10 = 5x2x1.
Looking at the prime factorization of these numbers, only one of them has a sum of factors between 5 and 7 and has them all be distinct. The factors of 8. So the three numbers are 1, 2, and 4. The median is 2.
Good clear explanation!
But why do all factors have to be distinct? Edit: Oh!! I just saw it in the question! 'three DISTINCT positive integers' sry must've just glossed over it not knowing its meaning. Your solution made me awear of what 'distinct' factors were, so thank you for that %)
Hey 9 is not 3×2×1. Its 3×3×1
I went with the process of elimination. (1,2,3) has a sum of 6. However its product of 6 does not meet the criteria. The only possible combination is (1,2,4) because of its sum of 7 and product of 8, which both meet the criteria.
Let the integers be a , b , c . then we have a b c as 8 or 9 or 10. since minimum value of a b c = 8 , then at least one of them is 1 . Suppose a = 1 . Since maximum of a + b + c is 7 and b c can be 8 or 10 we have ( b , c ) = { ( 2 , 4 ) , ( 2 , 5 ) } but if we have ( 2 , 5 ) is considered, a + b + c = 1 + 2 + 5 = 8 > 7 thus ( 2 , 4 ) is only possible. Hence ( a , b , c ) = ( 1 , 2 , 4 ) which have 3 terms. Thus median term = 2 3 + 1 = 2 and the second term in 1 , 2 , 4 is 2 which is the median.
I disagree with this sentence as it is phrased.
Since minimum value of a b c = 8 , then at least one of them is 1 .
Note that if we had a b c = 3 0 (because all that you're using is the minimum), then the statement is false.
What about 1,3,3? No one said the integers were all different. Right?
Problem Loading...
Note Loading...
Set Loading...
Five cannot be written as the sum of three distinct positive integers.
The only way to write six as a sum of three distinct positive integers is { 1 , 2 , 3 } ⟹ product = 6.
The only way to write seven as a sum of three distinct positive integers is { 1 , 2 , 4 } ⟹ product = 8.
Since the product cannot be 6, the product is 8. Therefore the numbers are { 1 , 2 , 4 } and the median is the central value, that is 2 □