Upper and Lower Bounds

Question 1:

When x = 1000 (1 s.f.) and
y = 60 (1 s.f.), find the upper bound of x + y

1115

Question 2:

When x = 2000 (1 s.f.) and
y = 6.98 (3 s.f.), find the lower bound of x - y

1493.015

Question 3:

When x = 0.808 (3 d.p.) and
y = 0.533 (3 d.p.), find the lower bound of x × y

0.42999375

Question 4:

When x = 6100 (2 s.f.) and
y = 90 (1 s.f.), find the upper bound of x ÷ y

72.352941176471