Upper and Lower Bound problem?

Question

Hey. I've got some questions on the topic of Upper and Lower bounds in which i have some difficulties with. All comments will be so much appreciated. Many thanks!

1. A car travels 5000m, correct to the nearest metre, in 2 minutes 21.7 seconds, correct to the nearest tenth of a second. Find the upper and lower bounds of the average speed in metres per second.

Regarding question 2 i found that at the end it requires you to divide certain upper bounds with certain lower bounds. I did convert the 2 minutes into 160 seconds and added it onto the 21.7. I found the upper and lower bounds by using add and sub and using 10 and 1/10 for the secnd. I used the speed = distance/time formula as i figured it was needed and got the values 35.30180021 m/s and 35.26984127 m/s. I was wondering becuase the question is asking for the speed i am suppose to divide the distance and time? In an examination what other formulas could appear on bounds?

Many thanks! All comments are so very much appreciated.

Answer 1

hi,

distance = 5000 m, correct to nearest meter

upper bound = 5001m

lower bound = 4999 m

also time = 2 min 21.7 sec, correct to nearest tenth of a second

=> time = 2*60 + 21.7 = 141.7 sec

upper bound = 141.8 sec

lower bound = 141.6 sec

now there will be 4 speeds 1.e., 1)upper/upper, 2)upper/lower, 3)lower/upper & 4)lower/lower

1)upper/upper => 5001/141.8 = 35.268

2)upper/lower => 5001/141.6 = 35.318

3)lower/upper => 4999/141.8 = 35.254

4)lower/lower => 4999/141.6 = 35.303

therefore from these 4 values, the upper bound for velocity is  35.318 and the lower bound is 35.254

Hope this is helpful. keep smiling. bye.