Question 9 - (3 marks available)

By rounding to 1 significant figure, estimate the answers to these questions:

a) 17 * 82

b) 54 x 671

c) 207 x 643

Answer: a) 1,600

b) 35,000

c) 120,000

Step-by-step explanation:

First, round each number to one significant digit (the first digit).

Then multiply them.

a) 17 - -> rounds to 20

82 - -> rounds to 80

20 x 80 = 2 x 8 with two zeros

= 1 6 0 0

b) 54 - -> rounds to 50

671 - -> rounds to 700

50 x 700 = 5 x 7 with three zeros

= 3 5 0 0 0

c) 207 - -> rounds to 200

643 - -> rounds to 600

200 x 600 = 2 x 6 with four zeros

= 1 2 0 0 0 0