Question

Look at the pyramid. The pair of adjacent cells in the bottom row add up to give the number in the corresponding top cell in the next row; and these two cells add upto give the number at the top of the pyramid. Write an algebraic expression to get the final answer.

• A. (x+1)
• B. 2(x+1)
• C. 3(x+1)
• D. 4(x+1)

Answer 1

The correct option is D

4(x+1)

Observe the numbers in the bottom row, they are consecutive natural numbers.
Let us take 2 = x , 3= (x+1) and 4 = ( x + 2 )
2 + 3 = 5 i.e. x + (x+1) = (2x +1 )
3 + 4 = 7 i.e. (x+1) + (x+2) = ( 2x +3)
5 + 7 = 12 i.e. (x+1) + (x+2)
= 4x + 4
= 4 (x +1)
If there are 3 consecutive numbers in the bottom row then the final answer will be 4 times the middle number i.e. 4(x+1)