Discover Mathematics P4: Term 1, Unit 5, Lessons 1–3
GoalTurn a comparison sentence into a multiplication equation and back.
New words
equation · a number sentence with an equals signproduct · the answer to a multiplicationfactor · a number that we multiply
Explanation
A comparison sentence can be written as an equation. The sentence 12 is 3 times as many as 4 says that 12 is made of 3 groups of 4, so 12 = 3 × 4. The big number is the product. The number of times and the small number are the factors. Use this pattern: big number = number of times × small number. The sentence 24 is 4 times as many as 6 becomes 24 = 4 × 6. We can also go the other way: 5 × 7 = 35 can be read as 35 is 5 times as many as 7, or 35 is 7 times as many as 5. When a letter stands for a number we do not know, we write it in the equation. Look at the words times as many, and do not mix them up with more than.
Sentence
Equation
12 is 3 times as many as 4
12 = 3 × 4
24 is 4 times as many as 6
24 = 4 × 6
35 is 5 times as many as 7
35 = 5 × 7
Worked examples
Write an equation: Omar has 6 books and his sister has 7 times as many. Her books are 7 × 6 = 42, so we write 42 = 7 × 6 and say 42 is 7 times as many as 6.
Equation
Sentence
56 = 8 × 7
56 is 8 times as many as 7
56 = 7 × 8
56 is 7 times as many as 8
Write a sentence for 56 = 8 × 7. It says 56 is 8 times as many as 7. It also says 56 is 7 times as many as 8. Both are true because of the commutative property: 8 × 7 = 7 × 8.
A bakery sells 9 cakes on Monday and 4 times as many on Friday. Friday: c = 4 × 9 = 36 cakes. Note that 36 is not 4 more than 9; 4 more than 9 is 13.
Class activity
Sentence match. Write six comparison sentences on slips of paper, such as 20 is 4 times as many as 5, and six matching equations on other slips. Mix them and match each sentence to its equation. Make two sentences that use more than and see why they do not match.
Practice
1
Write an equation: 32 is 4 times as many as 8.
32 = 4 × 8.
2
Write a sentence for 45 = 9 × 5.
45 is 9 times as many as 5 (or 5 times as many as 9).
3
Nour has 7 pens. Her friend has 3 times as many. Write an equation and solve it.
p = 3 × 7 = 21 pens.
4
A school has 12 teachers and 10 times as many pupils. Write an equation for the pupils.
p = 10 × 12 = 120 pupils.
5
Is 24 = 8 + 3 the same as saying 24 is 8 times as many as 3? Explain.
