Q&A - PSLE Math

[htn]

Best wishes[/quote]

After 70 blue marbles removed,
Ratio of blue marbles : white marbles = 3u : 4u

If 112 white marbles are removed, then blue marbles : white marbles
= 3u + 70 : 4u – 112


an alternative approach …

After 70 blue marbles removed,
Ratio of blue marbles : white marbles = 3u : 4u

If 112 white marbles are removed, then blue marbles : white marbles
= 3u + 70 : 4u – 112
= 8 : 7

Cross-multiply- 7 x (3u + 70) = 8 x (4u-112)
21u + 490 = 32u – 896
11u = 1386, 1u = 126

Number of blue marbles = 3u + 70 = 3 x 126 + 70 = 378 + 70 = 448
Number of white marbles = 4u = 4 x 126 = 504

When 48 more blue marbles are added, number of blue marbles = 448 + 48 = 496
Total number of marbles = 48 + 448 + 504 = 1000

Percentage of blue marbles = 496/1000 = 49.6%

cheers.[/quote]
Hi, why after If 70 blue marbles removed is 3u + 70
after If 112 white marbles are removed is 4u - 112

Thanks

[MathIzzzFun]

htn:

Best wishes

After 70 blue marbles removed,
Ratio of blue marbles : white marbles = 3u : 4u

If 112 white marbles are removed, then blue marbles : white marbles
= 3u + 70 : 4u – 112


an alternative approach ..

After 70 blue marbles removed,
Ratio of blue marbles : white marbles = 3u : 4u

If 112 white marbles are removed, then blue marbles : white marbles
= 3u + 70 : 4u – 112
= 8 : 7

Cross-multiply- 7 x (3u + 70) = 8 x (4u-112)
21u + 490 = 32u – 896
11u = 1386, 1u = 126

Number of blue marbles = 3u + 70 = 3 x 126 + 70 = 378 + 70 = 448
Number of white marbles = 4u = 4 x 126 = 504

When 48 more blue marbles are added, number of blue marbles = 448 + 48 = 496
Total number of marbles = 48 + 448 + 504 = 1000

Percentage of blue marbles = 496/1000 = 49.6%

cheers.[/quote]
Hi, why after If 70 blue marbles removed is 3u + 70
after If 112 white marbles are removed is 4u - 112

Thanks[/quote]

Hi

After 70 blue marbles removed, ratio of blue: red = 3u : 4u
so before the 70 blue marbles is removed, number of blue marbles = 3u + 70 = number of blue marbles at first.

So at first, number of blue : red = 3u + 70 : 4u
Remove 112 red marbles, and the ratio becomes 3u+70 : 4u-112

cheers.

[htn]

Hi, need help


Mrs Hoon made some cookies to sell. 3/4 of them were chocolate cookies and the rest were almond cookies. After selling 210 almond cookies and 5/6 of the chocolate cookies, she had 1/5 of the cookies left.

How many cookies did Mrs Hoon sell?
Thanks

[htn]

MathIzzzFun:

htn:

Best wishes

After 70 blue marbles removed,
Ratio of blue marbles : white marbles = 3u : 4u

If 112 white marbles are removed, then blue marbles : white marbles
= 3u + 70 : 4u – 112


an alternative approach ..

After 70 blue marbles removed,
Ratio of blue marbles : white marbles = 3u : 4u

If 112 white marbles are removed, then blue marbles : white marbles
= 3u + 70 : 4u – 112
= 8 : 7

Cross-multiply- 7 x (3u + 70) = 8 x (4u-112)
21u + 490 = 32u – 896
11u = 1386, 1u = 126

Number of blue marbles = 3u + 70 = 3 x 126 + 70 = 378 + 70 = 448
Number of white marbles = 4u = 4 x 126 = 504

When 48 more blue marbles are added, number of blue marbles = 448 + 48 = 496
Total number of marbles = 48 + 448 + 504 = 1000

Percentage of blue marbles = 496/1000 = 49.6%

cheers.

Hi, why after If 70 blue marbles removed is 3u + 70
after If 112 white marbles are removed is 4u - 112

Thanks[/quote]

Hi

After 70 blue marbles removed, ratio of blue: red = 3u : 4u
so before the 70 blue marbles is removed, number of blue marbles = 3u + 70 = number of blue marbles at first.

So at first, number of blue : red = 3u + 70 : 4u
Remove 112 red marbles, and the ratio becomes 3u+70 : 4u-112

cheers.[/quote]


Thanks

[MathIzzzFun]

htn:

Hi, need help


Mrs Hoon made some cookies to sell. 3/4 of them were chocolate cookies and the rest were almond cookies. After selling 210 almond cookies and 5/6 of the chocolate cookies, she had 1/5 of the cookies left.

How many cookies did Mrs Hoon sell?
Thanks

Hi

ratio of choc cookies : almond cookies
= 3:1
= 30u : 10u --> total cookies = 40u

After selling 5/6 choc cookies and 210 almond cookies, number of cookies left ;
choc cookies = 1/6 x 30u = 5u
almond cookies = 10u-210
total left = 5u + 10u -210= 15u - 210 = 1/5 of number at first = 1/5 x 40u = 8u
15u - 210 = 8u
7u = 210, 1u = 30
Total cookies sold = 4/5 x 40u = 4/5 x 40 x 30 = 960

cheers.

[raghupavithra]

gordon, kenneth and leon spent their money in the ratio 3:4:7 last month.this month,gordon’s expenditure increased while kenneth’s expenditure decreased. If gorden and kenneth spent the same amount this month while leon spent $350 more than gorden, what was the total expenditure of the three boys last month?


how to solve this? pls help me

[Suz855]

gordon, kenneth and leon spent their money in the ratio 3:4:7 last month.this month,gordon's expenditure increased while kenneth's expenditure decreased. If gorden and kenneth spent the same amount this month while leon spent $350 more than gorden, what was the total expenditure of the three boys last month?


My propose solution

[][][][][][]G\t\tK\t\tL
Last mth[]3\t\t4\t\t7
X2[][][][][]6\t\t8\t\t14
This mth[]7\t\t7\t\t7u+350

7u--> 350
1u -->50
Last mth\t28x50 = 1400

[chrisu]

Pls help to solve;


Complete the number pattern.
1, 2, 10, 37, 101, _____
(1) 138
(2) 158
(3) 226
(4) 246

Thanks.

[stary]

Hi all,


Can someone explain/show me the workings of this question?

http://www.flickr.com/photos/64113082@N03/6007585363/in/photostream
Ans: 5
(SCGS Prelim 2010 P6 Question 3)

Thanks!

[MathIzzzFun]

chrisu:

Pls help to solve;


Complete the number pattern.
1, 2, 10, 37, 101, _____
(1) 138
(2) 158
(3) 226
(4) 246

Thanks.

Hi

1 (+1^3) 2 (+2^3) 10 (+3^3) 37 (+4^3) 101 (+5^3) 226

cheers.