Page 177 - SK Year 5 Mathematics DLP

4 In 2020, the Intellect Building and Harmony Building are 0.4 decade and
2 decades old, respectively. When would the age of the Harmony Building
be equal to 3 times the age of the Intellect Building?

Solution In 2020, the Intellect Building is 0.4 decade old.
Harmony Building is 2 decades old.
I use the trial and
error method.
Age
The The Check
Intellect Harmony 0.5 decade
Building Building × 3

First Try 2021 0.5 decade 2.1 decades 1.5 decades

0.6 decade
× 3

Second Try 2022 0.6 decade 2.2 decades 1.8 decades
0.7 decade
× 3
Third Try 2023 0.7 decade 2.3 decades 2.1 decades
0.8 decade
× 3
Fourth Try 2024 0.8 decade 2.4 decades 2.4 decades

The fourth try was accurate.

What are the other methods
to check the answer?

The age of the Harmony Building will be 3 times the age of the
Intellect Building in 2024.

The age difference between Aneka Building and
Harmony Building is 0.1 century. What is the age, in decades,
of the Aneka Building in 2020?

• Emphasise to pupils to check the answers using different calculation 169
4.4.1 strategies such as multiplication for repeated addition and division
for repeated subtraction.