Question

A number, c, rounded to the nearest 10 is 640 . Another number, d, rounded to the nearest 10 is 420 . What are the lower and upper bounds of c+d?

Answer 1

LB : 1050

UB : 1070

Explanation:

When you round to the nearest 10, the error is 10÷2 = 5

So the first number's (c) bounds are 640 ± 5

Lower bound of c = 640 - 5 = 635

Upper bound of c = 640 + 5 = 645

The second number's (d) bounds are 420 ± 5

Lower bound of d = 420 - 5 = 415

Upper bound of d = 420 + 5 = 425

Now let's do what we're asked, LB and UB of c+d.

Lower bound (LB) of c+d = LB c + LB d = 635 + 415 = 1050

Lower bound (LB) of c+d = LB c + LB d = 635 + 415 = 1050Upper bound (UB) of c+d = UB c + UB d = 645 + 425 = 1070