2014_QNR 21. Neha has blocks with numbers printed on it. She makes a pyramid so that the sum of the two adjacent blocks is equal to the number on the block placed above them (as shown below). If she applies the same principle to make a pyramid of 15 blocks as shown below, what number must replace the question mark (?) ?
Ans: Let us start working from the lower blocks and up higher. We should be able to get the below figure after filling in the lower blank blocks:
[‘A’ is an assumption on the middlemost lower block as we don’t know what value might fit in]. From the figure we can conclude that (17+A) + (A+1) = 42 => 2A = 24. A= 12
From here, we should be able to get the below figure:
Hence, answer option (4).