Aaron walks 3 kilometres in 1 hour. How far can he walk in 5 hours?
Answer
Walking for 5 hours means covering the 1-hour distance 5 times.
Distance covered in 1 hour = 3 km
Distance covered in 5 hours = 5 × 3 km
= 3 + 3 + 3 + 3 + 3 km
= 15 km
Why it happens: multiplication is just repeated addition. Each new hour adds another 3 km to the total, so 5 hours add 3 km five times.
Q2.
Aaron’s pet tortoise walks at a much slower pace. It can walk only 1⁄4 kilometre in 1 hour. How far can it walk in 3 hours?
Answer
The speed is a fraction now, but nothing else changes — still multiply.
Distance in 1 hour = 1/4 km
Distance in 3 hours = 3 × 1/4 km
= 1/4 + 1/4 + 1/4 km
= 3/4 km
The tortoise can walk 3⁄4 km in 3 hours.
Tip: three quarter-kilometres make three-quarters of a kilometre — 750 metres. Still less than 1 km, which fits a slow tortoise.
Q3.
We saw that Aaron can walk 3 kilometres in 1 hour. How far can he walk in 1⁄5 hours?
Answer
One-fifth of an hour covers one-fifth of the 1-hour distance.
Distance in 1 hour = 3 km
Distance in 1/5 hour = 3 km divided into 5 equal parts
= 3 ÷ 5
= 3/5 km
So 1⁄5 × 3 = 3⁄5.
Why it happens: five stretches of 1⁄5 hour make one full hour. So five equal pieces of the distance must make 3 km, and each piece is 3⁄5 km.
Q4.
How far can Aaron walk in 2⁄5 hours?
Answer
Work in two steps — first one-fifth of an hour, then double it.
Step 1: distance in 1/5 hour = 3 ÷ 5 = 3/5 km
Step 2: 2/5 hour is twice 1/5 hour
Distance = 2 × 3/5
= 6/5 km = 1 1/5 km
So 2⁄5 × 3 = 6⁄5.
Tip: this is the whole method in a nutshell — divide by the denominator of the multiplier, then multiply by its numerator. Every fraction multiplication in this chapter follows these two steps.