Page 132 - NUMINO Challenge_C2

Basic Concepts The Cat that Catches Mice

10 cats catch 10 mice in 10 minutes. It takes 100
cats 10 minutes, not 100 minutes, to catch 100
mice.

A germ multiplies twice every day. When the germ is put in a jar, the jar
becomes full of bacteria in 10 days. The jar becomes half full in nine
days, one day before it becomes full.

Example There are three pieces of chain that are made of two linked rings.
It takes 10 minutes to cut a ring and put it back together. If you
want to make a circle of rings using the three pieces of chain, how
long will it take?

Class Notes minutes to disconnect and

As shown on the right, it takes
reconnect three chains.

But if you disconnect two rings from a chain and connect the
other chains, as shown on the diagram to the right, you need to
disconnect and reconnect only two rings. Therefore, it takes

minutes.

Therefore, it takes minutes to connect all the three chains.

Try It Again Two people eat two apples in two minutes. How long does it
take eight people to eat eight apples? Note that every person
eats apples at the same speed.

129Communication