Upper and Lower Bounds

Question 1:

When x = 93 (2 s.f.) and
y = 67 (2 s.f.), find the upper bound of x + y

161

Question 2:

When x = 1.61 (2 d.p.) and
y = 0.87 (2 d.p.), find the lower bound of x - y

0.73

Question 3:

When x = 6900 (2 s.f.) and
y = 72.3 (3 s.f.), find the upper bound of x × y

502832.5

Question 4:

When x = 6600 (2 s.f.) and
y = 730 (2 s.f.), find the lower bound of x ÷ y

8.9115646258503