Question

Round the following numbers to 2 significant figures:

a) 987
b) £432.75
c)
792 m

Answer 1

Answers:

• a) 990
• b) £430
• c) 790 m

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Step-by-step explanation:

The number 987 has three nonzero digits, showing that we have 3 sig figs here. But we want to round to 2 sig figs. This means we need to keep the 2 left-most digits, and drop the third one

We go from 987 to 980

But wait: we need to round to 990 instead since 987 is closer to 990 than it is to 980.

In other words, we round to the nearest tens place value in this case. A similar situation happens when we round 792 to 790

Also, 432.75 will round to 430

Notice that the zero at the end of something like 430 is not a significant digit. You can think of 430 as
`4.3 * 10^2` to see that the 4.3 now has 2 sig figs (meaning that 0 at the end is effectively just a placeholder more or less).