Upper and Lower Bounds

Question 1:

When x = 0.151 (3 d.p.) and
y = 3.821 (3 d.p.), find the upper bound of x + y

3.973

Question 2:

When x = 4000 (1 s.f.) and
y = 100 (1 s.f.), find the upper bound of x - y

4405

Question 3:

When x = 1490 (3 s.f.) and
y = 270 (3 s.f.), find the lower bound of x × y

400207.5

Question 4:

When x = 9010 (3 s.f.) and
y = 8000 (1 s.f.), find the upper bound of x ÷ y

1.202