Q&A - P5 Math

[MathIzzzFun]

Udon:

hi..need help :?:


Thank U....

Q1 The total number of balls in Box A and Box B is 165 less than the total number of balls in Box A and Box C. The number of balls in Box C is 4 times the number of balls in Box B. The number of balls in Box D is 3 times the total number of balls in Box A and Box B. If the total number of balls in all the 4 boxes is 752.

a) How many balls are there in Box A?

b) How many balls are there in Box D?

\"The total number of balls in Box A and Box B is 165 less than the total number of balls in Box A and Box C.\" --> draw a model and one will see that there are 165 more balls in Box C than Box B

Box C - Box B = 165 --> 3 units (since Box C is 4 times Box B, difference is 3 units)
Solving, Box B --> 55, Box C --> 220
Box D --> 3A + 165

Total Box A+ Box B+ Box C+ Box D --> A+55+220+3A+165 = 752
A --> 78
D --> 399

Box A --> 78
Box B --> 55
Box C --> 220
Box D --> 399

cheers.

[ozora]

need some guide in this questions.

Rob saved 40% less than Perry.
Lucy saved 30% less than Rob.
If Lucy saved $210, how much did Perry save?

Is Rob or Perry 100%? Why?

[MathIzzzFun]

ozora:

need some guide in this questions.

Rob saved 40% less than Perry.
Lucy saved 30% less than Rob.
If Lucy saved $210, how much did Perry save?

Is Rob or Perry 100%? Why?

You can set either to be 100%.

eg.
1) Perry --> 100%, Rob --> 60%, Lucy --> 0.7 x 60% = 42%
42% --> $210, Perry --> 210/42 x 100 = $500

2) Rob --> 100%, Perry --> 100/60 x 100% = 500/3 %, Lucy --> 70%
70% --> $210, Perry --> 500/3 x 210/70 = $ 500

3) using ratio
Rob : Perry = 60:100 = 3:5
Rob : Lucy = 100 : 70 = 10 : 7
Rob : Perry : Lucy --> 30 : 50 : 21
Perry --> 50/21 x $210 = $500

cheers.

[ozora]

1.The number of basketballs was 3/5 of the number of footballs. In jan , 1/3 of the basketball and 1/3 of the football were sold. In feb,4 basketball n 4 footballs were sold. The number of basketballs left was 1/2 of the number of footballs. How many basketballs were there at first?


2.Andy, Bryan and calvin decided to share to buy a present. The total of Andy’s and Bryan’s to Calvin’s share was 7:2. The total of Bryan’s and. Calvin’s share to Andy’s share was 2:3. Andy paid $19 more than Bryan. Find the cost of the present.

Thanks for guiding in advance.

[ozora]

MathIzzzFun:

ozora:

need some guide in this questions.

Rob saved 40% less than Perry.
Lucy saved 30% less than Rob.
If Lucy saved $210, how much did Perry save?

Is Rob or Perry 100%? Why?

You can set either to be 100%.

eg.
1) Perry --> 100%, Rob --> 60%, Lucy --> 0.7 x 60% = 42%
42% --> $210, Perry --> 210/42 x 100 = $500

2) Rob --> 100%, Perry --> 100/60 x 100% = 500/3 %, Lucy --> 70%
70% --> $210, Perry --> 500/3 x 210/70 = $ 500

3) using ratio
Rob : Perry = 60:100 = 3:5
Rob : Lucy = 100 : 70 = 10 : 7
Rob : Perry : Lucy --> 30 : 50 : 21
Perry --> 50/21 x $210 = $500

cheers.

Thanks

[ozora]

Need guide in this question only: The number of basketballs was 3/5 of the number of footballs. In jan , 1/3 of the basketball and 1/3 of the football were sold. In feb,4 basketball n 4 footballs were sold. The number of basketballs left was 1/2 of the number of footballs. How many basketballs were there at first?


Thanks

[verykiasumummy]

ozora:

Need guide in this question only: The number of basketballs was 3/5 of the number of footballs. In jan , 1/3 of the basketball and 1/3 of the football were sold. In feb,4 basketball n 4 footballs were sold. The number of basketballs left was 1/2 of the number of footballs. How many basketballs were there at first?


Thanks

just trying to help.

The number of basketballs was 3/5 of the number of footballs.

means ratio of basket:foot is 3:5.

In jan , 1/3 of the basketball and 1/3 of the football were sold.

so ratio has to be multiplied by 3.
basket : foot
9 : 15
-3u -5u
---------------
6 : 10

In feb,4 basketball n 4 footballs were sold.

basket : foot
6 : 10
-4 -4
---------------
1 : 2

since 6u-2u=4u, and 10u-2u=8u, which is exactly half, therefore

2u --> 4
1u --> 2
at first there were 9u basketball, so
9u --> 18

ans is 18.

[KP2]

Need help with Nanyang primary 2011 SA2 paper 2 question no 16.

[ozora]

verykiasumummy:

ozora:

Need guide in this question only: The number of basketballs was 3/5 of the number of footballs. In jan , 1/3 of the basketball and 1/3 of the football were sold. In feb,4 basketball n 4 footballs were sold. The number of basketballs left was 1/2 of the number of footballs. How many basketballs were there at first?


Thanks

just trying to help.

The number of basketballs was 3/5 of the number of footballs.

means ratio of basket:foot is 3:5.

In jan , 1/3 of the basketball and 1/3 of the football were sold.

so ratio has to be multiplied by 3.
basket : foot
9 : 15
-3u -5u
---------------
6 : 10

In feb,4 basketball n 4 footballs were sold.

basket : foot
6 : 10
-4 -4
---------------
1 : 2

since 6u-2u=4u, and 10u-2u=8u, which is exactly half, therefore

2u --> 4
1u --> 2
at first there were 9u basketball, so
9u --> 18

ans is 18.

think there is a mistake. the subtraction of basket is 6u-1u =5u .
therefore cannot be half.

[lotto]

KP2:

Need help with Nanyang primary 2011 SA2 paper 2 question no 16.

Hi KP2,

If this is the question that u mean,

Mr Chen bought some pencil cases and bags for the children at a gathering. The price of each pencil case was $2.40 while the price of each bag was $10.80. For every 4 bags bought, he was given one such pencil case for free. After receiving the free pencil cases, the number of pencil cases was 1/3 of the number of bags bought.
If Mr Chen paid a total of $1584, how much more did he pay for the bags
than the pencil cases?

The solution is as follow:

Let's say if he didn’t buy any pencil case with money, the ratio of pencil cases to bags would be 1 : 4. However the ratio in the end is 1 : 3.

In my working, I assume that at first he bought bags and get the free pencil cases and then after that he bought the pencil cases.

At first -> Pencil case : Bags = 1 : 4
In the end -> Pencil case : Bags = 1 : 3

Since the number of bags is the same, u must make them to the same unit.
At first -> 3: 12
In the end -> 4: 12

From there, u can see that the ratio of pencil cases and bags that he bought using money is 1 : 12
1u × $2.40 + 12u × $10.80 = $132u
$1584 ÷ $132 = 12 (1 unit)
Pencil cases = 1 u = 12
Price of pencil cases = 12 × $2.40 = $28.80
Bags = 12 u = 144
Price of bags = 144 × $10.80 = $1552.20
$1555.20 - $28.80 = $1526.40

The answer key is wrong I think :scratchhead:
Hope mine is correct and can be understood.
But it is way too messy :imsorry:
I'm still not use to post solution here