Upper and Lower Bounds

Question 1:

When x = 3.7 (2 s.f.) and
y = 40 (1 s.f.), find the upper bound of x + y

48.75

Question 2:

When x = 0.7 (1 d.p.) and
y = 0.33 (2 d.p.), find the lower bound of x - y

0.315

Question 3:

When x = 10.4 (1 d.p.) and
y = 0.62 (2 d.p.), find the upper bound of x × y

6.53125

Question 4:

When x = 88.4 (3 s.f.) and
y = 11 (2 s.f.), find the upper bound of x ÷ y

8.4238095238095