Question

Which one of the following is an even number?
A. 198^7
B. 19x98
C. 19^87
D. 1+9+87

I know I can just solve each one but is there a faster way?

Answer 1

You don't have to solve each one, and you don't even need a calculator if you understand the following rules for <i>integer</i> calculations:
Multiply: only odd*odd will give odd
power: only odd to any power will give odd
Add/subtract: only odd±even will give odd.
Note: for add/subtract, when you have three operands, work out answer in two steps.

Try a few numerical examples for each rule, and you'll have the rules at your disposal for the rest of your math career.