Find the digit represented by ? in the following problem: 37? × 35 = 13090. No calculators, please.
I did it "mentally", but then my brain is cluttered with various trivia . . .Find the digit is represented by in the following problem: .
No calculators, please.
I saw that: .
. . So that: . . . . which is 140 short of 13,090
. . Hence, we need four more 35's.