P6 Algebra questions

Question 1: Simplify the algebraic expression below

(Adapted from 2018 SNG Primary 6 CA1 Math Paper 1 Question 3)

9 + 5g – 2 + 4g = ?

Answer:

9 + 5g – 2 + 4g (Step 1: Group the numbers together, then the terms)
= 9 – 2 + 5g + 4g (Step 2: Simplify the equation)
= 7 + 9g

Question 2: Write an algebraic expression

(Adapted from 2018 Maha Bodhi Primary 6 CA1 Math Paper 1 Question 6)

Don is 11 years old. He is f years older than Donki.
How old is Donki?

Answer:

Since Don is older, Donki must be the younger one.

Age of Donki = (11 – f) years old

Question 3: Solve an algebraic equation by substitution

(Adapted from 2018 ACS Primary 6 CA1 Math Paper 1 Question 8)

Find the value of 4y – (y + 3)/2 + 10 when y = 5.

Answer:

4y – (y + 3)/2 + 10 (Step 1: Replace y with 5)
= (4 x 5) – (5 + 3)/2 + 10 (Step 2: Use order of operation. Solve the brackets first)
= 20 – 8/2 + 10 (Step 3: Solve the division part next)
= 20 – 4 + 10 (Step 4: Solve the subtraction part)
= 16 + 10 (Step 5: Solve the addition part)
= 26

Word problem sum 1: Write simple algebraic equation and simplify them

(Adapted from 2018 Nanyang Primary 6 CA1 Math Paper Question 29)

The mass of a bag of rice is n kg.
The mass of a baby is twice as heavy as the bad of rice.
The mass of a school bag is 5 kg more than the mass of the baby.
What is the mass of the school bag? Give your answer in terms of n.

Answer:

Mass of the baby = 2n
Mass of the school bag = (2n + 5) kg

Word problem sum 2: Higher level algebra challenge

(Adapted from 2018 Nanyang Primary 6 CA1 Math Paper Question 14)

Alvin had $10y. He had $24 less than Claire. Linda had half as much as Alvin. They bought a birthday cake for their mum which cost $(4y+5).

a. How much did they have altogether at first?
Give your answer in terms of y in the simplest form.

b. If y = 7, how much did they have left in total after buying the birthday cake?

Answer to part a:

Amount of money that Claire has = $(10y + 24)

Amount of money that Linda has = $(10y/2) = $5y

Amount of money that they had at first = $10y + $10y + $24 + $5y = $(25y + 24)

Answer to part b:

Amount of money that they had at first = $25y + 24 = ($25 x 7) + $24 =  $175 + $24 = $199

Cost of the birthday cake = $(4y + 5) = ($4 x 7) + $5 = $28  + $5 = $33

Amount of money they have left after buying the birthday cake = $199 – $33 = $166

Bonus Primary 6 Algebra Practice Question:

(Adapted from PSLE Math paper 2018)

XYZ Police Post received reports of 16 scams, 2n scams and 2 + n scams monthly for the period of October to December respectively.

“The number of scam cases happened in October.”
Is the sentence above True, False or Impossible to Tell?

Answer:

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