Q&A - PSLE Math

[JE382]

Can anyone help answer these questions? I need the working as I don't understand the questions.


1) Roy, Sam and Ted had a sum of money. Roy had 80% of Sam's money. Sam had 60% of Ted's. After Roy gave $12 to Sam, he had 5/7 of what Sam had. How much more money did Ted have than Sam in the end?

2) Neil and Paul had different sums of money. If Neil spent $40 each week and Paul spent $80 each week, Neil would still have $1040 left when Paul spent all his money. If Neil spent $80 each week and Paul spent $40 each week, Neil would still have $320 left when Paul spent all his money. How much did Paul have at first?

3)Jerry bought four times as many pencils as notebooks and spent a total of $21.60. He spent $2,40 more on notebooks than the pencils. Given that a notebook costs $3.20 more than a pencil, find the cost of a pencil.

4) Ms Lee baked 24 more chocolate muffins than banana muffins. After she gave away 1/6 of the chocolate muffins and 3/8 of the banana muffins,she was left with 35 more chocolate muffins than banana muffins. How many chocolate muffins did she bake at first?

5) At first, Ravi had $200 more than Vincent. He gave 40% of his money to Vincent. Vincent then gave 25% of his money to Ravi. In the end, Vincent had $68 more than Ravi. How much did Vincent give Ravi?

:thankyou:

[JE382]

One more question :

In the figure that is not drawn to scale, ABCF is a rectangle. Find the area of the shaded parts.
http://i44.tinypic.com/10s9jfb.png\">

[tianzhu]

JE382:

5) At first, Ravi had $200 more than Vincent. He gave 40% of his money to Vincent. Vincent then gave 25% of his money to Ravi. In the end, Vincent had $68 more than Ravi. How much did Vincent give Ravi?

Hi

Good Morning.

I assume that calculators would be allowed for this question. You may draw MD to show the transactions or choose to work using units.

At first
Ravi ----- 20 units + 200
Vincent ------20 units

I use 20 units instead of 10 units to avoid working with decimals during future transfer.

Ravi gave 8 units + 80 to Vincent. He was left with 12 units + 120

Vincent now had 28 units + 80

Vincent then gave 25% of his money to Ravi.
25% ------- 7 units + 20

In the end
Ravi --------- 19 units + 140
Vincent ------- 21 units + 60

19 units + 140 + 68 ------ 21 units + 60
1 unit ----- 74

Vincent gave (7*74) + 20 or 538 to Ravi.

Best wishes

[tianzhu]

JE382:

4) Ms Lee baked 24 more chocolate muffins than banana muffins. After she gave away 1/6 of the chocolate muffins and 3/8 of the banana muffins,she was left with 35 more chocolate muffins than banana muffins. How many chocolate muffins did she bake at first?

Hi

Good Morning.

A common multiple of 6 and 8 is 24

At first
Banana muffins ----- 24 units
Chocolate muffins ----- 24 units + 24

She gave away 1/6 of the chocolate muffins and 3/8 of the banana muffins

In the end
Banana muffins ----- 15 units
Chocolate muffins ----- 20 units + 20

She was left with 35 more chocolate muffins than banana muffins.

15 units + 35 ------ 20 units + 20
5 units ------ 15
1 unit ------ 3

Number of chocolate muffins at first ----- (24*3) + 24 ------ 96

Best wishes

[oliveminx]

JE382:

One more question :

In the figure that is not drawn to scale, ABCF is a rectangle. Find the area of the shaded parts.
http://i44.tinypic.com/10s9jfb.png\">

Did u draw this diagram yourself or was it scanned from the original question?

[tianzhu]

JE382:

One more question :

In the figure that is not drawn to scale, ABCF is a rectangle. Find the area of the shaded parts.
http://i44.tinypic.com/10s9jfb.png\">

Hi

It’s helpful to have a bigger image.Is line BE a straight line?

In answering this question, I assume that line BE is a straight line
The two shaded areas are of equal sizes.

Area of triangle ABD ----- ½ * 12 * 9 ------ 54
Area of triangle (height 7 cm) ----- ½ * 12 * 7 ------ 42

Difference of 1 shaded part ------ 54 – 42 -----12
Area of 2 shaded parts ------ 12*2 ----- 24

Best wishes

[tianzhu]

JE382:

2) Neil and Paul had different sums of money. If Neil spent $40 each week and Paul spent $80 each week, Neil would still have $1040 left when Paul spent all his money. If Neil spent $80 each week and Paul spent $40 each week, Neil would still have $320 left when Paul spent all his money. How much did Paul have at first?

Hi

A similar type of question was discussed in an earlier post.

Doris and Annie have each planned a list of words to learn,
If Doris learnt 40 words per day while Annie learnt 20 words per day, Doris would have 70 words left to learn while Annie had completed learning all the words.
If Doris learnt 20 words per day while Annie learnt 40 words per day, Doris would have 130 words left to learn while Annie had completed learning all the words.
How many words do Doris and Annie have to learn respectively?

Please follow this link.

page 293@Wed Apr 13, 2011 9:07 am
http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=69&t=280&start=2920


For your question, please study the example as shown in the earlier solution; you should be able to get.

Case 1
Neil ----- 1 unit + 1040
Paul ----- 2 units

Case 2
Neil ----- 4 unit + 320
Paul ----- 2 units

1 unit + 1040 ---------- 4 unit + 320
3 units ----- 720
1 unit ----- 240

Paul had 2 units or 480 at first.

Best wishes

[tianzhu]

JE382:

3)Jerry bought four times as many pencils as notebooks and spent a total of $21.60. He spent $2,40 more on notebooks than the pencils. Given that a notebook costs $3.20 more than a pencil, find the cost of a pencil.

Hi

You may use MD or present your solution using Number*Value in tabulated form.

Due to time constraints, I shall give you some pointers for you to draw the MD.

Amount spent on pencils ----- (21.6 - 2.4)/2 ----- 9.6\t
Amount spent on note books ----- 12

9.6/4 ----- 2.4
12 – 2.4 ----- 9.6

Each notebook costs $3.2 more than a pencil.

Number of notebooks ----- 9.6/3.2 ----- 3

Number of pencils ----- 12

Cost of 1 pencil ----- 9.6/12 ------ 0.8

Best wishes

[tianzhu]

JE382:

1) Roy, Sam and Ted had a sum of money. Roy had 80% of Sam's money. Sam had 60% of Ted's. After Roy gave $12 to Sam, he had 5/7 of what Sam had. How much more money did Ted have than Sam in the end?

Hi

It’s helpful to draw some simple pictorial representation to show the relationships among the three people.

Consider Roy and Sam first

In the beginning

Roy had 80% of Sam's money.

Roy ----- 4 units ----- 16 units
Sam ----- 5 units ----- 20 units
Total ----- 9 units ----- 36 units

After the transfer of $12 from Roy to Sam.

Roy ----- 5 units ----- 15 units
Sam ----- 7 units ----- 21 units
Total ----- 12 units ----- 36 units

A common multiple is 36.Make the total number of units the same as the amount of money(Roy and Sam) stays the same.

1 unit ---- 12

At first, Sam had (20*12) or 240

60% ----- 240
100% ----- 400

At first, Ted had 400.

In the end Sam had (21*12) or 252

Ted's amount of money stays the same before and after.

Hence, Ted had (400-252) or 148 more than Sam in the end.

Best wishes

[maychang]

oliveminx:

JE382:

One more question :

In the figure that is not drawn to scale, ABCF is a rectangle. Find the area of the shaded parts.
http://i44.tinypic.com/10s9jfb.png\">

Did u draw this diagram yourself or was it scanned from the original question?

Hi Oliveminx,
Thanks for your reply.
JE382 is my DD, she is going to sit for psle next year.
She draws the diagram herself as we do not have a scanner at home.
Will get her to repost the diagram in bigger size.