Pyramid Investigations 2 – Consecutive Number Pyramids

Algebra Level 1

Using the pattern above as an aid, evaluate the sum:

1 + 2 + 3 + 4 + 5 + 4 + 3 + 2 + 1 1 + 2 + 3 + 4 + 5 + 4 + 3 + 2 + 1

This problem is part of the Pyramid Investigations Set .


The answer is 25.

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18 solutions

Prasun Biswas
Mar 29, 2014

Refer to the solution of this problem which suggests that 1 + 2 + 3 + . . + ( n 1 ) + n + ( n 1 ) + . . . + 3 + 2 + 1 = n 2 1+2+3+..+(n-1)+n+(n-1)+...+3+2+1=n^2 .

Using that we can say ----->

1 + 2 + 3 + 4 + 5 + 4 + 3 + 2 + 1 = 5 2 = 25 1+2+3+4+5+4+3+2+1 = 5^2 = \boxed{25}

25

Lathikesh Vtk - 7 years, 2 months ago

1^2=1 ; 2^2=4; 3^3= 9 ; 4^2= 16 ; 5^2 = 25; so 25 is the answer

Mainak Zaman - 7 years, 2 months ago

5+(4+1)+(4+1)+(2+3)+(2+3)=25

Maya Patil - 7 years, 2 months ago

good

Abid Ali - 7 years, 2 months ago

Ridiculously easy.

Rafael Da Silva Pereira - 7 years, 2 months ago

25

Sadia Safa - 7 years, 2 months ago

1+2+3+4+5+4+3+2+1=25

Jasveen Sandral - 7 years, 2 months ago

25

Rini Mitra - 7 years, 2 months ago

1+2+3+4+5+4+3+2+1=5+2(1+2+3+4) 5+2(10)=25

Ayush Sharma - 7 years, 2 months ago

25

Honeyia Sipra - 7 years, 2 months ago

25

Mohanish Patel - 7 years, 1 month ago

Ans is 25

Mahrukh Huma - 7 years, 2 months ago

25

Arkajit Pal Choudhury - 7 years, 2 months ago
Abhishek Agrawal
Mar 31, 2014

always mid term square here 5 so 5 square is equal to 25

25

Treasure Irum - 7 years, 2 months ago

25

Akbar Ali - 7 years, 2 months ago
Raven Herd
Mar 30, 2014

if we see , the sequence is 1^2,2^2,3^2,4^2,5^2.Therefore, 1,4,9,16 ,25.

It's easy...............

Tanzir Hasan Mahim - 7 years, 2 months ago
Afzal Sajid
Mar 29, 2014

5^5=25

r u sure 5^5=25 or 3125

Archies Dubey - 7 years, 2 months ago
Bhavesh Bhagde
Mar 29, 2014

1+2+3+4+5+4+3+2+1=25

25

Archies Dubey - 7 years, 2 months ago

Here is a seris...

1^2=1

2^2=4

3^2=9

4^2=16

5^2=25

Steven Brown
Mar 22, 2015

If we are on term four, then the number is just h^2 = 16. So the next term is h^2 + 2h + 1, or (h + 1)^2 = 25

Matt George
Dec 15, 2014

Square the no.of Items in the Center of the Pyramid.

1+2+1= 2^{2}=4 1+2+3+2+1=3^{2}=9 1+2+3+4+3+2+1=4^{2}=16 there fore, 1+2+3+4+5+4+3+2+1=5^{2}=25

Arya Ukunde
Apr 30, 2014

1+2+3+4+5+4+3+2+1 = (1+4)+(2+3)+(5)+(4+1)+(3+2) = 5+5+5+5+ 5 = 5*5 = 25

Vikash Yadav
Apr 20, 2014

ans can be find out by the maximum value in the question and just square it . in our question max. value is 5 after squaring it .we get 25 as our answer alternatively just add those values given in the question as 1+2+3+4+5+4+3+2+1=25.

Subham Sarkar
Apr 18, 2014

look at the number exactly at the middle of patterns. (easiest,fastest way to think) 1+2+3+4+5+4+3+2+1 5 is the exactly middle number. Now, just square it. 5^2
you get the answer 25.

Krishna Garg
Apr 16, 2014

Applying formula NXN that is maximum number is 5X5 =25 Ans K.K.GARG.India

Krantiveer Singh
Apr 8, 2014

if the middle term is n then use ( ) n times and add two in every term as ( 1)+(1+2)+(1+2+2)+(1+2+2+2)+(1+2+2+2+2) no of 2 in nth term will be (n-1) answer is 25

Roha Nehas
Apr 3, 2014

terribly easy...should have been a challenge!

Christine Teng
Apr 3, 2014

Just add the numbers up! 2(1+2+3+4)+5=25

Moshiur Mission
Apr 3, 2014

n(n+1)/2+(n-1)n/2 = (n^2+n+n^2-n)/2 = n^2, here n=5 so result is 25

Navin Ramisetty
Apr 1, 2014

n(n+1)/2 + n(n-1)/2 =n^2

nice

chiranjit kuiry - 7 years, 2 months ago

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