Upper and Lower Bounds

Question 1:

When x = 1400 (2 s.f.) and
y = 2730 (3 s.f.), find the lower bound of x + y

4075

Question 2:

When x = 5.639 (3 d.p.) and
y = 0.75 (3 d.p.), find the upper bound of x - y

4.89

Question 3:

When x = 9.835 (3 d.p.) and
y = 433.5 (1 d.p.), find the lower bound of x × y

4262.764025

Question 4:

When x = 4000 (1 s.f.) and
y = 72.7 (3 s.f.), find the upper bound of x ÷ y

61.94081211287