chap 3 (approximation & estimation

when to use the wavy =

only when estimating (rounding up or down) when the degree of accuracy is not stated

how to present rounding of numbers

use = sign, and state degree of accuracy bracketed beside the answer. for example, (3s.f.), (nearest hundreds)

Cheryl says that 5192.3 is equal to 519 when rounded off to the nearest 10. She drops '2' because it is less than 5. Do you agree? Explain your answer.

No. She needs to put a "0" in the ones place holder after dropping "2".

Weiming says that 8.395 is equal to 8.4 when rounded off to two decimal places because he thinks that 8.40 is the same as 8.4. Do you agree? Explain your answer.

8.40 is rounded off to two decimal places which is more accurate than 8.4 which is rounded of to one decimal place.

we count significant figures from…

the first non-zero number starting from the left.

what are the five rules to significant numbers.

1. All non-zero digits are significant. 2. All zeros between non-zero digits are significant. 3. In a decimal, all zeros before a non-zero digit are not significant. 4. In a decimal, all zeros after a non-zero digit are significant. 5. The zeros at the end of a whole number may or may not be significant depending on how the number is rounded off.

round 0.004 709 89 to 4 s.f.

0.004 709 89 = 0.004 710 (4s.f.)

0.0999 99 to 2 s.f.

0.099 99 = 0.10 (2s.f.)

numbers in general are to be rounded off to..(when not specified in question)

3 s.f.

money is to be rounded off to…(when not specified in question)

nearest cents

angles are to be rounded off to…(when not specified in question)

1 d.p.