The problem asks us to fill in the blanks with either $g$ (grams) or $kg$ (kilograms) to make the statements reasonable.

1. Problem Description

The problem asks us to fill in the blanks with either $g$ (grams) or $kg$ (kilograms) to make the statements reasonable.

2. Solution Steps

a) The book is about 100 ___ heavy.

A typical book weighs more than 100 grams, so 100 $g$ would be too light. 100 $kg$ is extremely heavy. Thus, the answer should be grams (likely 100s of grams, but 100 $g$ is closest.)

Answer: $g$.

b) The packet of sugar is 1 ___ heavy.

A packet of sugar likely weighs around 1 kilogram.

Answer: $kg$.

c) The teaspoonful of salt is about 5 ___ heavy.

A teaspoonful of salt weighs only a few grams. Thus, it is about 5 $g$.

Answer: $g$.

d) We need 10 ___ of mealie meal per month.

Mealie meal is a staple food, so a household would need a substantial amount of it each month. Thus, it is more appropriate to use kilograms.

Answer: $kg$.

3. Final Answer

a) $g$

b) $kg$

c) $g$

d) $kg$