All concepts combined
Primary 5 Decimals study guide: the whole chapter, step by step
About this subtopic
This mixed practice stop brings together 3 topics from Primary 5 Decimals: Decimals by tens, Units and the decimal point, Two units in one question. Nothing on the question says which topic it comes from, so choosing the method is part of the skill.
Practice questions with worked solutions
Question 1 is free to try. The other 2 open in the free trial, each with its full working.
Print this subtopic · included with a plan
2 more questions, each with its full working.Answers checked, progress kept, wrong ones come back in revision. No card needed.
Start the 7-day free trialQuestion 1 of 3 · Intermediate · free to tryTwo identical crates are stacked on a bench in a store room. The top of the…Two identical crates are stacked…
Two identical crates are stacked on a bench in a store room. The top of the upper crate is 1.7 m above the floor. One crate is taken off the bench. The top of the crate still on the bench is 138 cm above the floor. How high is the bench? Give your answer in metres.
Show the working and the answer
Working
- 1.7 m = 1.7 × 100 = 170 cm
- height of one crate = 170 − 138 = 32 cm
- height of the bench = 138 − 32 = 106 cm
- 1 m = 100 cm
- 106 cm = 106 ÷ 100 = 1.06 m
Answer: 1.06 m
For parents
How can my child keep the units straight in P5 decimals mixed practice?
Each question here gives its measurements in two different units, and the answer in a third form.
What your child learns here
Each question here gives its measurements in two different units, and the answer in a third form. Heights are given in metres and centimetres, cord is cut in centimetres from rolls measured in metres, and glue is bottled in litres and asked for in millilitres. Your child changes the units at the right moment and calculates with decimals in between, using the Primary 5 Decimals outcome on converting a measurement between a smaller and a larger unit in decimal form.
- Change every measurement into one unit before adding, subtracting or comparing.
- 100 cm make 1 m, so 1.7 m is 170 cm and 106 cm is 1.06 m.
- 1000 ml make 1 litre, so 0.35 L is 350 ml.
- When pieces must come from one roll, divide to find whole pieces per roll and keep the leftover.
- Give the final answer in the unit the question asks for, even if the working used another.
Does the answer make sense?
An answer in millilitres must be 1000 times the same amount in litres. One carton holds 20 bottles of 0.35 L, which is 7 L, so 7000 ml is right and 700 ml or 70 ml shows a conversion that moved too few places.
How to practise these questions
All three questions are Intermediate. The bench question gives the top of two stacked crates in metres and the top of one crate in centimetres, so the height of one crate comes from the difference before the bench can be found. The cord question cuts 90 cm pieces from 8 m rolls for 25 blinds and asks what is left on the last roll opened. The glue question multiplies 0.35 L by 20 bottles and gives the carton in millilitres. Ask your child to write the unit beside every number in the working; a number without a unit is where a conversion is usually lost.
Questions parents ask
When should my child change the units? Before the first calculation that combines two measurements. Adding 1.7 m to 138 cm without changing one of them mixes two sizes of unit.
Is it better to work in the smaller unit? Often, because the numbers become whole. 170 cm and 138 cm are easier to subtract than 1.7 m and 1.38 m. Change back at the end if the answer needs metres.
What does the leftover cord question test? Dividing a roll into whole pieces and keeping the remainder. Each 8 m roll gives 8 pieces of 90 cm with 80 cm left over, and that leftover cannot be joined to the next roll.