Toby tries to work out the answer to 311 * 1.9 using the calculator.
He gets an answer of 5909.
a) Without using a calculator, estimate 3.11 * 1.9 by rounding each number to 1 significant figure. Is Toby's answer sensible?
b) Use a calculator to work out the actual answer. Use this to explain what Toby may have done wrong.
a) Rounding 3.11 to 1 significant figure gives 3, and rounding 1.9 to 1 significant figure gives 2. Multiplying these gives an estimate of 6. This is significantly lower than Toby's answer of 5909, so his answer is not sensible.
b) Using a calculator to work out the actual answer gives 5.909. It appears that Toby may have accidentally multiplied 311 by 19 instead of 1.9, which would explain why his answer is so much larger than the actual answer.