Q&A - PSLE Math
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lizawa:
Hi lizawahi tianzhu.
the area refers to the white space labeled A,B and C, or the area of the circle A, B, C ?
lizawa
I believe it refers to the areas of circle A,B and C. -
Hi tianzhu,
my son said this type of question normally refers to unshaded part of A:B:C
Do you have the answer ?
Is it : 25:18:1 ? -
Solution
Total area of cirlces
(B+C) : A
= 4:5
= 24:30
1/6 of A shaded -> 1/6 * 30 = 5 units shaded
unshaded A -> 30 units - 5 units = 25 units
unshaded (B+C) -> 24 - 5 = 19 units
Can draw model here, to see clearer.
B has 5 units, C has 3 units. Size of units in B and C are different.
5 units of B + 3 units of C -> 24
1 unit of B + 1unit of C -> 5
3 units of B + 3 units of C ->15
2 units of B -> 24 - 15 = 9
unshaded B = 4 units of B -> 9 * 2 = 18
2 units of C -> 24 - 18 - 5 = 1
unshaded C = 2 units = 1
unshaded
A:B:C
= 25:18:1 -
Hi lizawa
Thanks
The answer listed in the worksheet is 20:15:1 -
[quote]The answer listed in the worksheet is 20:15:1
[/quote]then, in that case, it's asking for the total area of A : B:C
Extension to the above solution,
unshaded B = 18
total B = 22.5
unshaded C =1
total C = 1.5
A:B:C
30:22.5 : 1.5
= 60:45:3
= 20:15:1 -
Hi, lizawa
Thanks for your help. -
Q1) Alan had some apples. When he packed them into bags of seven apples, he would have 3 apples left. When he packed them into bags of nine apples, he would be short of 6 apples. What was the least number of apples that Alan had?
This problem may be solved by listing and Guess and Check which are tedious.
Wish to seek help from members who may be aware of any more effective method. -
is this ok?
10+ (7* ?) = 10 + 78 = 66
3 + (9 ?) = 3 + 9*7 = 66
if kids know their times table well, this is fast. -
ks2me:
Hi ks2meis this ok?
10+ (7* ?) = 10 + 7*8 = 66
3 + (9* ?) = 3 + 9*7 = 66
if kids know their times table well, this is fast.
Please elabrate more, why 10+, ......? -
pardon me if my brain thinks too simply...
i used the first sequence as (7+3) + 7 + 7 + 7........... so 10 + (7*?)
and second as (9-6) + 9 + 9 + 9 .................. so 3 + (9*?)
10 + (7*?) = 3 + (9*?)
7 + (7* ?) = 9*?
can do?