Upper and Lower Bounds

Question 1:

When x = 80 (1 s.f.) and
y = 98.9 (3 s.f.), find the lower bound of x + y

173.85

Question 2:

When x = 100 (1 s.f.) and
y = 47.5 (3 s.f.), find the lower bound of x - y

47.45

Question 3:

When x = 1.7 (3 s.f.) and
y = 230 (2 s.f.), find the upper bound of x × y

400.675

Question 4:

When x = 0.279 (3 d.p.) and
y = 0 (1 d.p.), find the upper bound of x ÷ y

-5.59