🎯 Practise smarter · 1 min read
Always check your answer
Estimate first, substitute back, and ask: does this answer make sense?
Estimate before you calculate
Round the numbers and get a rough answer first. 4.9 × 21 is about 5 × 20 = 100, so an answer of 1,029 must be wrong (the real answer is 102.9).
Substitute back
For equations, put your answer back into the original question. If 2x + 7 = 19 and you got x = 6: 2 × 6 + 7 = 19 ✓.
Ask: does it make sense?
A person can't be 250 years old. A probability can't be more than 1. A discount can't make the price go up. A length can't be negative.