Upper and Lower Bounds

Question 1:

When x = 0.127 (3 d.p.) and
y = 7.5 (1 d.p.), find the lower bound of x + y

7.5765

Question 2:

When x = 1000 (1 s.f.) and
y = 50 (1 s.f.), find the lower bound of x - y

895

Question 3:

When x = 4000 (1 s.f.) and
y = 3150 (3 s.f.), find the lower bound of x × y

11007500

Question 4:

When x = 628.3 (1 d.p.) and
y = 0.59 (2 d.p.), find the upper bound of x ÷ y

1074.1025641026