Q&A - P5 Math

[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

[ozora]

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

Anyone can help?

[lotto]

ozora:

verykiasumummy:

[quote=\"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.[/quote]
@ozora:
try to use units and parts to continue from the table given! u can find that 2u = 4

@verykiasumummy:
your steps to get '2u = 4' is not so reliable. if the number is not so nice, u might not be able to guess the '2u'
Nice one btw :celebrate:

[cimman]

ozora:

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

Anyone can help?

ozora, check your pm. verykiasumummy's solution is correct, though as Lotto has said, it is not so easy to 'see'. Most children will not be able to 'see' that 2u = 4 and if the numbers are larger, it is not easy to process.