Question

Lance wrote down a lot of plus sevens and minus fours. Altogether he wrote 22 digits. When he came to add them all up the total was zero. How many plus sevens were there?

Answer 1

So, when solving this: you’ll want to consider multiples of 7 and 4.

7,14,21,28
4,8,12,16,20,24,28

If you write four +7’s and seven -4’s, they cancel out. Given that that is 11 digits, do it twice and you have your answer.

Eight +7’s
Fourteen -4’s