Upper and Lower Bounds

Question 1:

When x = 8 (1 s.f.) and
y = 807 (3 s.f.), find the upper bound of x + y

816

Question 2:

When x = 1.331 (3 d.p.) and
y = 0 (1 d.p.), find the upper bound of x - y

1.3815

Question 3:

When x = 0.121 (3 d.p.) and
y = 0.89 (2 d.p.), find the upper bound of x × y

0.1087425

Question 4:

When x = 9.7 (1 d.p.) and
y = 0.565 (3 d.p.), find the upper bound of x ÷ y

17.271922054916