RemeliaMaths Year 4 Measurement
Year 4 converting units of measure
The objective: Convert between different units of measure (km→m; hour→minute).
The explanation, example and questions are the ones Remelia uses in the app; the questions are not taken from any test paper.
The idea
Converting is multiplying or dividing by the conversion factor. Which one depends on which way you are going.
How to do it
- Bigger unit to smaller unit: multiply, because you get more of them.
- Smaller to bigger: divide.
- Know: 1 km = 1000 m, 1 m = 100 cm, 1 hour = 60 minutes.
A worked example
3 km = 3 × 1000 = 3000 m. 2 hours = 2 × 60 = 120 minutes.
Watch for
Dividing when you should multiply. Ask: should the number get bigger or smaller? 3 km in metres must be a bigger number.
Try four questions
-
Convert 9.5 kg into g.
Show the answer to question 1
Answer: 9,500 g
Why:
1 kg = 1000 g, so 9.5 × 1000 = 9,500 g.
-
Which is longer: 3 km or 300 m?
- A 300 m
- B 3 km
- C They are the same length
Show the answer to question 2
Answer: B · 3 km
Why:
Put both in the same unit. 3 km is 3,000 m, which is longer than 300 m.
-
Convert 2 cm into m.
Show the answer to question 3
Answer: 0.02 m
Why:
100 cm = 1 m, so 2 ÷ 100 = 0.02 m.
-
How many millilitres of lemonade are in the jug?
Show the answer to question 4
Answer: 700 ml
Why:
The numbered marks go up in 1 l, which is 1,000 ml. Nine unnumbered marks split each gap into ten equal steps, so each mark is 1,000 ÷ 10 = 100 ml.
The top of the lemonade is seven marks up from the bottom: 7 × 100 = 700 ml.
Answers
- 1. 9,500 g
- 2. B · 3 km
- 3. 0.02 m
- 4. 700 ml
The mistakes Remelia names
When a wrong answer to a question like these matches one of these mistakes, the app says what the child seems to have done before they try again.
- Question 1, the answer 0.0095: It looks as if you divided instead of multiplying. A smaller unit takes more of them to make the same amount, so the number gets bigger: the digits move to the left.
- Question 1, the answer 95,000: Your digits are right, but in the wrong columns: your answer is 10 times too big.
- Question 1, the answer 950: Your digits are right, but in the wrong columns: your answer is 10 times too small.
- Question 2, the answer A · 300 m: It looks as if you compared the numbers without their units. A bigger number can be a smaller amount when its unit is smaller: write both in the same unit first, then compare.
- Question 3, the answer 200: It looks as if you multiplied instead of dividing. Dividing by 10, 100 or 1,000 makes a number smaller: the digits move to the right.