Decimals

NZ Level 5

Problem solving with decimals II

Lesson

We frequently encounter situations that involve decimals in everyday life. For example, amounts of money are a combination of whole numbers (dollars) and decimals (cents). We also often use decimals in weights and heights. Let's look at some examples of word problems that involve the decimals skills you have already learnt.

Remember to think about what operations you will need to answer a question.

**Evaluate:** Jay is $1.76$1.76m tall, Maggie is $1.43$1.43m tall and Tan is $1.6$1.6m tall. What is the average height of the three students to $2$2 decimal places?

**Think: **To find the average, we need to add up all the values then divide the answer by the number of values.

**Do: **

$1.76+1.43+1.6$1.76+1.43+1.6 | $=$= | $4.79$4.79 |

$4.79\div3$4.79÷3 | $=$= | $1.59666$1.59666 ... |

$=$= | $1.60$1.60m ($2$2d.p) |

**Evaluate: **How many $0.26$0.26 litre glasses can a $20.8$20.8 litre water bottle fill?

**Think:** We can write this as a division problem- $20.8\div0.26=80$20.8÷0.26=80.

**Do:** $80$80 glasses can be filled

**Evaluate:** A car travels $6.3$6.3m in $10$10 seconds. How far will it travel in $5$5 minutes? Give your answer in kilometres.

**Think: **To work out how far the car travels in $1$1 minute, we would do $6.3\times6=37.8$6.3×6=37.8m

To work out how far the car travels in $5$5 minutes, we would do $37.8\times5=189$37.8×5=189m

To convert this answer from metres to kilometres, we would do $189\div1000=0.189$189÷1000=0.189km

**Do:** The car would travel $0.189$0.189km

A calculator is $8.9$8.9 cm long. How far will $130$130 calculators reach if laid end to end? Give your answer in metres.

Three items weighing $3.41$3.41 kg, $2.58$2.58 kg and $5.79$5.79 kg are to be posted but are found to be overweight. By how much does the total weight exceed the $11.38$11.38 kg limit?

How many $0.17$0.17 L containers can be filled from a tank which holds $2.38$2.38 L?

Understand operations on fractions, decimals, percentages, and integers