revision: CH 1 - Approximations and estimations

APPROXIMATIONS-
a) 7.8126 = 8 to the nearest whole number.
       ^ this figure is 5 or more = you round up, if it is less that 5 = you round down.
b) 7.8126 = 7.81 to three significant figures.
           ^ this figure is less than 5 = you round down.
c) 7.8126 = 7.813 to three decimal places.
             ^ this figure is more than 5 = round up.
d) 0.078126 = 0.0781 to three significant figures.
         ^ 7 is the first significant figure.
e) 3596 = 3600 to two significant figures.
        ^ This figure is 5 or more.
[Zero (0) is not a significant figure!!]


ESTIMATION-
Look at the question. If it says 1s.f., it means to estimate to 1 significant figure.
We have 57.2 x 110/2.146 x 46. To estimate to 1s.f., we have to ---->
Make it approximately 50 x 100/2 x 50 which approximately equals 50. And that would be our estimate.

Actual answer -> 62.52 (to 4 s.f.)

1. Estimate to 1 s.f.
a) 7.2 x 9.8 -> 7 x 10 = 70 [Actual answer -> 70.56]
b) 2.03 x 58.6 -> 2 x 60 = 180 [Actual answer -> 118.958]