Q&A - PSLE Math

[Michaelia0816]

Pls help with this question,

1) A number has 3 digits. When it is divided by 6 or 7, it leaves a remainder of 1. When it is divided by 8 or 11, it leaves a remainder of 7. What is the largest such number?

2) A rectangle of length 24 cm is given as shown below. Twelve identical isoceles triangles are cut from it. The perimeter of the remaining figure is 120 cm more than that of the rectangle. Find the perimeter of an isoceles triangle?

Picture of the figure for Q2:
http://t.co/lUBjqv11

[Michaelia0816]

2632parent:

Need help on this simple question, I just cannot get the answer.


1) A piece of raffia measuring 7 m long was cut into smaller pieces. Each piece was 5/8 m long. What is the length of the remaining raffia?

Thank you.

Hi, this is the simple question,

Solution:
7m=700cm
5/8m= 62.5 cm
700cm/62.5cm=11 Remainder 12.5 cm

Answer: 12.5 cm

[tianzhu]

Michaelia0816:

Pls help with this question,

1) A number has 3 digits. When it is divided by 6 or 7, it leaves a remainder of 1. When it is divided by 8 or 11, it leaves a remainder of 7. What is the largest such number?

Hi

You may use “SL” to do this question.

Find multiples of 42 + 1

Similarly find multiples of 88 + 7

Do a listing, the answer is 799.

I believe you can use your calculator for this question, so with a bit of planning, it’s not too tedious.

Another way, with some reasoning you can see that the multiple of 88 must be greater than the multiple of 42 by 82 so as to satisfy the condition in the question.

880 – 82 ------ 798

So the number is 798 + 1 ------ 799

Best wishes

[Michaelia0816]

tianzhu:

Michaelia0816:

Pls help with this question,

1) A number has 3 digits. When it is divided by 6 or 7, it leaves a remainder of 1. When it is divided by 8 or 11, it leaves a remainder of 7. What is the largest such number?

Hi

You may use “SL” to do this question.

Find multiples of 42 + 1

Similarly find multiples of 88 + 7

Do a listing, the answer is 799.

I believe you can use your calculator for this question, so with a bit of planning, it’s not too tedious.

Another way, with some reasoning you can see that the multiple of 88 must be greater than the multiple of 42 by 82 so as to satisfy the condition in the question.

880 – 82 ------ 798

So the number is 798 + 1 ------ 799

Best wishes

How do you get it?

[Michaelia0816]

This answer is found on yahoo,



3-digi number divided by 6, remainder = 1
3-digi number divided by 7, remainder = 1

SO,
The 3-digi number divided by (6x7)42, remainder = 1

The largest 3-digit number = 42 x 23=
= 966+1 = 967 ........................................… [1]

Also,
3-digi number divided by 8, remainder = 7
3-digi number divided by 11, remainder = 7

The 3-digi number divided by (8x11)88, remainder = 7

The largest 3-digit number = 88 x 11=

= 968+7 = 975 ........................................… [2]

From [1] and [2].

975-88 = 887-88 = 799 >=====================< ANSWER

How to get 23 and 11?

[tianzhu]

Michaelia0816:

2) A rectangle of length 24 cm is given as shown below. Twelve identical isoceles triangles are cut from it. The perimeter of the remaining figure is 120 cm more than that of the rectangle. Find the perimeter of an isoceles triangle?

Picture of the figure for Q2:
http://t.co/lUBjqv11

Hi

Where is this question from?

Let the base of the isosceles triangle be b and each slanting side be s.

b ------ 24/6 ------ 4

24s -------- 120 + 48 ------- 168

s ----- 7

Perimeter of an isosceles triangle -------- 7+7+4 ------ 18

Best wishes

[charsen]

2) A rectangle of length 24 cm is given as shown below. Twelve identical isoceles triangles are cut from it. The perimeter of the remaining figure is 120 cm more than that of the rectangle. Find the perimeter of an isoceles triangle?


Picture of the figure for Q2:
http://t.co/lUBjqv11[/quote]
Check this solution
http://i49.tinypic.com/16baqmt.jpg

[tianzhu]

Michaelia0816:

How do you get it?

Hi

Where is this question from?Is this a typical PSLE type of question?

Are you comfortable with using the \"SL\" way to solve this question.

As for the alternative, I've no time to do the slide now.

Try to figure out on your own first.

Best wishes

[Michaelia0816]

Thx, pls help with the upper question.

[its888me]

Need help in the question below:


At first Alvin had twice as many trading cards as Steven. After Alvin had given away 285 of his trading cards, Steven had twice as many trading cards as Alvin. How many trading cards did they have altogether at first?

Answer is 845 but my child said it should be 570.

Can someone help? Thanks a lot in advance!