Helpful math tricks?

question: How much was response 2 amplified by? response 1:4.74 response 2: 7.03

Does anyone have any good tricks or ways to think about mathematical percentages overall? Specifically for this case I would double 4.7ish and since the second response is lower I would just shoot for an answer less than 50%, which usually Is good enough since its multiple choice (thank god) but if I needed a more specific answer...anyone got any mental tips or tricks?

if you have any other ones as well, I get bogged down converting natural logs as well....