Upper and Lower Bounds

Question 1:

When x = 13.42 (2 d.p.) and
y = 30.5 (1 d.p.), find the upper bound of x + y
43.975

Question 2:

When x = 616 (3 s.f.) and
y = 10 (1 s.f.), find the lower bound of x - y
600.5

Question 3:

When x = 9000 (1 s.f.) and
y = 300 (1 s.f.), find the upper bound of x × y
3325000

Question 4:

When x = 5000 (2 s.f.) and
y = 60 (1 s.f.), find the upper bound of x ÷ y
91.818181818182