a-b where a=8 to 1 s.f. and b=4.18 to 2 d.p.
- I thought a would be:
Upper:8.5 Lower:7.5
- And b would be:
Upper:4.185 Lower:4.175
However, I am not entirely sure if this is correct nor where to go after this step? Can anyone complete the problem and explain why I am incorrect?
the answer should be:
3.315≤a-b<4.325
Your bounds are correct. The upper bound for $a - b$ is obtained by subtracting the lower bound for $b$ from the upper bound for $a$, which gives $8.5 - 4.175 = 4.325$. The lower bound for $a - b$ is obtained by subtracting the upper bound for $b$ from the lower bound for $a$, which I will leave for you to complete.