Upper and Lower Bounds

Question 1:

When x = 800 (2 s.f.) and
y = 79 (2 s.f.), find the upper bound of x + y

884.5

Question 2:

When x = 10.6 (1 d.p.) and
y = 6.71 (2 d.p.), find the upper bound of x - y

3.945

Question 3:

When x = 3840 (3 s.f.) and
y = 92.1 (3 s.f.), find the lower bound of x × y

353011.75

Question 4:

When x = 93.7 (3 s.f.) and
y = 61.2 (3 s.f.), find the upper bound of x ÷ y

1.5331152902698