GB-03-04-001 · Checking an estimate
Sam says that 37 × 23 is 85. Use an estimate to show that Sam is wrong.
Checking by Estimation (Lower Bound Estimate)
Application of related method — Booklet p. 39
Method
1) Round both numbers to 1 significant figure
2) Multiply the rounded values and compare with the claimed answer
Worked Example (GB-03-04-001)
1)
Round both factors down to 30 and 20.
2)
The product is at least 600, so 85 is too small.
Ans =
The product is at least 600, which is greater than 85.