Upper and Lower Bounds

Question 1:

When x = 0.58 (2 d.p.) and
y = 0.645 (3 d.p.), find the lower bound of x + y

1.2195

Question 2:

When x = 21.22 (2 d.p.) and
y = 11 (1 d.p.), find the upper bound of x - y

10.275

Question 3:

When x = 600 (1 s.f.) and
y = 220 (2 s.f.), find the upper bound of x × y

146250

Question 4:

When x = 4990 (3 s.f.) and
y = 200 (1 s.f.), find the lower bound of x ÷ y

19.94