Estimation

Page 1

Decimal places

rather than rounding off to the nearest whole number, you might need to be a little more accurate. You might need to include some of the digits after the decimal point. 5 or more, we 'round up', 4 or less, it stays as it is.

Page 2

Significant figures

Another method of giving an approximated answer is to round off using significant figures.

With the number 368249, the 3 is the most significant digit, because it tells us that the number is 3 hundred thousand and something. It follows that the 6 is the next most significant, and so on.

With the number 0.0000058763, the 5 is the most significant digit, because it tells us that the number is 5 millionths and something. The 8 is the next most significant, and so on.

With numbers such as 30245, the 3 is the first significant figure and 0 the second, because of its value as a place holder.

Page 3

Bounds and limits

Bounds are thehighest possible value and lowest possible value of a number when it is rounded

A piece of wood is 12cm long to the nearest cm

It must be at least 11.5cm, it must be less than 12.5cm

11.5cm is the lower bound and 12.5cm is the upper bound for the length of the piece of wood.