Mathematics for IGCSE & O level - Estimation (Section 2 - No. 43)
In the process of estimation, when you calculate 4.7 * 1.9, what do you do first?
Use a calculator.
Round each number to 1 s.f.
Multiply the numbers as they are.
Round each number to 2 d.p.
Forklaring
In estimation, the first step is to round each number to one s.f.