Math Riddle II: What is Your Answer?

A graphic shows a series of numbers and asks readers to fill in the final blank. How would you solve this equation and what answer do you think is best?

Let’s take a look at the problem and some possible solutions.

As seen in the image below, the following riddle provides the following problem:

If:
2 = 6
3 = 12
4 = 20
5 = 30
6 = 42
Then:
9 = ??

How would you solve this quiz?

Our Answer: 90

The answer of 90 is achieved if we multiply the number on the left by one number higher than itself. Thus:

#	# +1	Product
2	x3	6
3	x4	12
4	x5	20
5	x6	30
6	x7	42
9	x10	90

It has also been presented as squaring the number and then adding the number, so for example: 2×2 = 4 + 2 = 6.

Other Answers

We’ve seen others come up with answers such as 72 and 56, using different methods than above.

An answer of 72 is reached if 9 is multiplied by 8. The reason for 8 would be that it is next incrementally in the middle column. (3, 4, 5, 6, 7, 8).

A few people have claimed it should be 56 by looking at the pattern formed by the right column. We hesitate to make assumptions that the right column would continue following the pattern before it while the left column does not.

Your Turn

Which solution did you come up with? Let us hear from you in the comments below.

Updated June 14, 2015
Originally published April 2013