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Primary 4 Mathematics · Chapter 4 · Answers and explanations

Lesson 4.4: Change on a Line Graph, and Choosing a Graph (answers)

Section A · Multiple choice 4 marks

1. Between which two months did Rina's savings decrease the most?1 mark

Rina's Savings0102030405060708090100JanFebMarAprMayJunSavings ($)
(A) January and February(B) May and June(C) March and April(D) April and May
Answer: (B) May and JuneSavings went down: Feb to Mar by 10, Apr to May by 10, and May to Jun by 70 − 30 = 40. The greatest decrease is May to June.

2. By how much did Rina's savings increase from March to April?1 mark

Rina's Savings0102030405060708090100JanFebMarAprMayJunSavings ($)
(A) $80(B) $20(C) $30(D) $10
Answer: (C) $30March: $50. April: $80. 80 − 50 = 30. (80 is just the April value.)

3. Between which two weeks did the water level increase the most?1 mark

Water Level in a Pond0102030405060708090100Week 1Week 2Week 3Week 4Week 5Water level (cm)
(A) Week 1 and Week 2(B) Week 3 and Week 4(C) Week 4 and Week 5(D) Week 2 and Week 3
Answer: (D) Week 2 and Week 3Increases: Week 1 to 2 is 10 cm, Week 2 to 3 is 90 − 70 = 20 cm. The level went down after Week 3. The greatest increase is Week 2 to Week 3.

4. Which graph is best for showing how the temperature changed through the day?1 mark

(A) Line graph(B) Bar graph(C) Table(D) Pictogram
Answer: (A) Line graphA line graph shows change over time, so you can see when it goes up or down.

Section B · Write your answer 11 marks

5. By how much did Rina's savings decrease from April to May?1 mark

Rina's Savings0102030405060708090100JanFebMarAprMayJunSavings ($)
Answer: $10April: $80. May: $70. 80 − 70 = $10.

6. Which graph is best to compare how many books 5 pupils read? Give a reason.1 mark

Answer: Bar graph, because the bars are easy to compare by heightA bar graph puts each pupil in a separate bar, so you can compare the heights.

7. Which is best to show exact numbers in rows and columns for easy reading?1 mark

Answer: TableA table lists the exact numbers in rows and columns, so there is no need to estimate from a graph.

8. Between which two weeks did the pond's water level decrease the most? By how many centimetres?1 mark

Water Level in a Pond0102030405060708090100Week 1Week 2Week 3Week 4Week 5Water level (cm)
Answer: Week 4 and Week 5, 35 cmDecreases: Week 3 to 4 is 90 − 80 = 10 cm. Week 4 to 5 is 80 − 45 = 35 cm. The greatest is Week 4 to Week 5.

9. How much did Rina save in January and February in all?1 mark

Rina's Savings0102030405060708090100JanFebMarAprMayJunSavings ($)
Answer: $100January: $40. February: $60. 40 + 60 = $100.

10. Between which two months was the greatest increase in Rina's savings? Write the amount.2 marks

Rina's Savings0102030405060708090100JanFebMarAprMayJunSavings ($)
Answer: March and April, $30Increases: Jan to Feb 20, Mar to Apr 30. Other changes go down. The greatest increase is $30 from March to April.

11. Here the graph is drawn up to Week 4. In Week 5 the water level is 45 cm. Where is the Week 5 point? How many centimetres below the Week 4 point is it?2 marks

Water Level in a Pond0102030405060708090100Week 1Week 2Week 3Week 4Water level (cm)
Answer: Halfway between 40 and 50; 35 cm below45 cm is halfway between 40 and 50. Week 4 is 80 cm, so 80 − 45 = 35 cm below.

12. Ravi wants to show how the number of visitors in a park changed every hour from 9 a.m. to 3 p.m. Mei wants to compare the number of visitors on 4 different days. Name the best graph for each pupil.2 marks

Answer: Ravi: line graph. Mei: bar graphRavi's data changes over time, so a line graph shows ups and downs. Mei wants to compare separate days, so a bar graph is best.
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