Upper and Lower Bounds

Question 1:

When x = 600 (1 s.f.) and
y = 30 (1 s.f.), find the lower bound of x + y

575

Question 2:

When x = 80 (1 d.p.) and
y = 0.589 (3 d.p.), find the lower bound of x - y

79.3605

Question 3:

When x = 86.96 (2 d.p.) and
y = 4.587 (3 d.p.), find the lower bound of x × y

398.8191075

Question 4:

When x = 7.104 (3 d.p.) and
y = 0.913 (3 d.p.), find the lower bound of x ÷ y

7.776135741653