Consulting Case Interview Practice Questions

Answer: C - 168 softballs. Although this is not a difficult problem, and could be calculated mentally, perhaps by multiplying 14 by 10 (140), then adding 2 more 12s to the answer.

However, there is a trick that allows you to multiply numbers close to ten together within seconds.

First, consider the problem: 14 x 12
Using the 2 in 12, add it to 14: 16 (these are the first two digits of the answer).
Using the 2 in 12, multiply it by the 4 in 14: 8 (this is the last digit of the answer).
Thus, the answer to 14 x 12 is 168.

It works for larger numbers in the teens, but those involve “carrying”.
Consider the problem: 17 x 14.
Using the 4 in 14, add it to 17: 21
Using the 4 in 14, multiply it by the 7 in 17 (28). The 8 is the last digit of the answer. Carry the 2 over, and add it to the 21 from the previous step to get 23. The answer to 17 x 14 is 238.

Key Takeaway: Sometimes you will find it necessary to multiply numbers in the teens together. With practice, this strategy will allow you to perform that calculation mentally, both quickly and accurately.

Again, this is a trick that requires lots of practice that works for some, and doesn’t work for others.