Estimating
We can use significant figures to get an approximate answer to a problem.
We can round off all the numbers in a maths problem to 1 significant figure to make 'easier' numbers. It is often possible to do this in your head.
- Question
Find a rough answer to
- Answer
We first round off both numbers to 1 significant figure (s.f.):
19.4 = 20 (1 s.f.)
0.0437 = 0.04 (1 s.f.)
So we now need to make the denominator a whole number. We can do this by multiplying both 20 and 0.04 by 100.
Divide everything by 4.
The real answer to 19.4 ÷ 0.0437 = 443.9359... So this was a good estimate.
Try this one. Remember, the working you do is just as important as the answer.
- Question
How would you get an approximate answer for 386062 × 0.007243?
- Answer
Did you get the answer 400000 × 0.007 = 2800?
If so, well done! You rounded off correctly and worked out the approximate answer.
Rounding to 1 s.f.
386062 = 400000
0.007243 = 0.007
So 400000 × 0.007 = 2800
Now try a Test Bite:Foundation or Higher
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