Too Many Numbers To Be Added!

Algebra Level 1

What is the sum of all number in the yellow square in the above multiplication table?


The answer is 3025.

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12 solutions

Kay Xspre
Mar 27, 2016

( i = 0 10 i ) v e r t i c a l × ( i = 0 10 i ) h o r i z o n t a l = 55 × 55 = 3025 \underbrace{(\sum_{i=0}^{10}i)}_{vertical}\times\underbrace{(\sum_{i=0}^{10}i)}_{horizontal}=55\times55 = 3025

Note : We use the fact that 1 + 2 + 3 + + n = 1 2 n ( n + 1 ) 1 + 2 + 3 + \cdots + n = \dfrac 12 n(n+1) .

I did a mistake and got the question wrong but my method was just fine. I noticed the increment of 55 so I did ((550+55)/2)*10 to find my answer.

Zachary Wolf - 5 years, 2 months ago
Caique Harger
Mar 28, 2016

Ignore the Zeros. On the first row we have 1+2+3+4+5+6+7+8+9+10=55= X On the second row we have 2X, third row 3X..... Sem it all you have 55X = 3025

This is also how i did it.

David Giblin - 5 years, 2 months ago
Ashish Menon
Mar 31, 2016

We observe that in each row, the sum of the numbers are n = 0 10 n x \displaystyle \sum_{n=0}^{10} nx where x x is the corresponding number in the 1 s t 1^{st} column. For example in in row 2 2 , the sum of numbers is n = 0 10 2 n \displaystyle \sum_{n=0}^{10} 2n .

So, we have to evaluate n = 0 10 n + 2 n + 3 n + + 9 n + 10 n \displaystyle \sum_{n=0}^{10} n+2n+3n+ \cdots + 9n + 10n .
= n = 0 10 ( 10 × 11 2 ) n \displaystyle \sum_{n=0}^{10} (\dfrac {10 ×11}{2})n
= n = 0 10 55 n \displaystyle \sum_{n=0}^{10} 55n = 3025 \boxed {3025} .

Stefan Lim
Apr 2, 2016

Sum of Row 0 and Row 10 is 550.

R o w 0 + R o w 10 = R o w 1 + R o w 9 Row 0 + Row 10 = Row 1 + Row 9 R o w 1 + R o w 9 = R o w 2 + R o w 8 Row 1 + Row 9 = Row 2 + Row 8 This pattern continues through the table. (0 and 10, 1 and 9, 2 and 8, 3 and 7, 4 and 6) 550 × 5 = 2750 550 \times 5\ = 2750 Sum of Row 5 is 275 2750 + 275 = 3025 2750 + 275 = 3025

Caeo Tan
Apr 1, 2016

We have 1+2+3+4+5+...+100 =1(1+2+...+10)+2(1+2+3+...+10)+3(1+2+...+10)+...9(1+2+3+...+10)+10(1+2+3+...+10) =(1+2+3+4+5+6+7+8+9+10)(1+2+3+4+5+6+7+8+9+10) =55*55=3025

Siddharth Tejpal
Mar 29, 2016

Second row = 11x5 Third row = 22x5...... Till last row = 110x5 Take 5 common 5(11+22+33.....110) take 11 common =5x11(1+2+3.....10) =55(55) =3025

Rafi Davis
Mar 28, 2016

You've got numbers from 1 to 10 in the problem and since it's a multiplication square you end up multiplying all the different numbers which is like when you're expanding double brackets the inside and then the outside. Anyway in the end it's just the sum of 1 to 10 squared which is 55 squared which is 3025

Joe Freeman
May 19, 2016

Each column is equal to the bottom number multiplied by half the size of the column. 11 numbers in each column makes it: 5.5*(10+20+30+40+50+60+70+80+90+100)

Hannes Camitz
Apr 12, 2016

11+110, 22+99....=121 in each pair. 5x121=605 605x5=3025

I know it's a bit blunt but it worked.

Andrea Mitta
Apr 3, 2016

You can also do it by assuming that in each row the sum of all the numbers will be a 10 + a 10 2 a*10+\frac {a*10}{2} where a a is a number from 1 to 10. For instance, the sum of the 10 row is 550 + 50 550+50 , thus you can consider using only the column a 5 a*5 sum all its numbers and multiplying the result by 10 you obtain 2750 2750 . At this point you have to add the value of the 5 column to find the answer to this problem 2750 + 275 = 3025 2750+275=\boxed{3025} .

Chacon Alexandre
Apr 1, 2016

S = 5×(1+10) + 5×(2+20) + 5×(3+30) + 5×(4+40) + 5×(5+50) +....+ +... + 5×(10+100)

= (5 + 10 + 15 + 20 + 25 +...+ 50) + (50 +100 + 150 + 200 +...+ 500) =

= 5×(5+50) + 5×(50+500) = 25+250+250+2500

ans: 3025

Kyle Birr
Mar 29, 2016

10! Sqared is how I solved it. Or 10 factorial Sqared.

10 ! = 3.6288 × 1 0 6 10! = 3.6288×10^6 . If you squared them, I think the value will be huge.

Kay Xspre - 5 years, 2 months ago

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