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primary 6 | Maths | Data Analysis
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CJ
CJ

primary 6 chevron_right Maths chevron_right Data analysis chevron_right Singapore

Pls help. Thks.

Date Posted: 3 years ago
Views: 178

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a)
a ★ b = 3a + 2b = 3 × a + 2 × b
So what this operation does is : it multiplies the left term by 3, multiplies the right term by 2, then adds them together.
It is easier to do the operation for the terms in the bracket first. Then perform the operation for the term outside and the result in the brackets.
Likewise to above,
5p ★ (4q ★ 3q)
= 5p ★ (3 × 4q + 2 × 3q)
= 5p ★ (12q + 6q)
= 5p ★ 18q
= 3 × 5p + 2 × 18q
= 15p + 36q (shown)
b)
If p = 1/5 and q = 3,
Then 5p ★ (4q ★ 3q) = 15p + 36q
= 15 × 1/5 + 36 × 3
= 3 + 108
= 111

Note : when you see a number directly on the left of a bracket, it is the same as doing multiplication on the bracket's terms.
Eg. 2(3) = 2 × 3
Eg. 6(3 + a) = 6 × (3 + a) = 6 × 3 + 6 × a = 18 + 6a
So you could also answer part a) like this :
5p ★ (4q ★ 3q)
= 5p ★ (3(4q) + 2(3q))
= 5p ★ (12q + 6q)
= 5p ★ 18q
= 3(5p) + 2(18q)
= 15p + 36q
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J
J's answer
1022 answers (A Helpful Person)
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J
J
3 years ago
Alternative working to a) ,if you start the operation from the outside first :

5p ★ (4q ★ 3q)

= 3 × 5p + 2 × (4q ★ 3q)

= 15p + 2 × (3 × 4q + 2 × 3q)

= 15p + 2 × (12q + 6q)

= 15p + 2 × 18q

= 15p + 36q (shown)


Alternative working for b) without using the result in a) :


If p = 1/5 and q = 3,

Then 5p ★ (4q ★ 3q)

= 5 × 1/5 ★ ( (4 × 3) ★ (3 × 3) )

= 1 ★ (12 ★ 9)

= 1 ★ (3 × 12 + 2 × 9)

= 1 ★ (36 + 18)

= 1 ★ 54

= 3 × 1 + 2 × 54

= 3 + 108

= 111