Tutor MathsGuru: Ask me for your burning Maths questions!

[YumYum]

Hi, I need help with the following Qn:


Prema, Tanya and Violette have 960 beads altogether. Prema gave some of her beads to Tanya and the number of Tanya's beads was doubled. Then Tanya gave some of her beads to Violette and the number of Violette's beads was doubled. If the 3 girls had the same number of beads in the end, how many beads did Prema have at first?

Thanks a lot!

[corneyAmber]

http://i55.tinypic.com/121tkio.jpg\">

[small]

ksi:

http://i55.tinypic.com/121tkio.jpg\">

Hi ksi,

There was an error. I think you deducted wrong; it should be 960-160-240 = 560.

Prema had 560 beads at first

[YumYum]

Dear Small & KiasuGrandmaster,


Thank you for the reply. Yes, the answer given in the wksheet was 560.

Warm Rgds.

[corneyAmber]

small:

ksi:

http://i55.tinypic.com/121tkio.jpg\">

Hi ksi,

There was an error. I think you deducted wrong; it should be 960-160-240 = 560.

Prema had 560 beads at first

Yes you are right, careless mistake....since original of tanya is 240, my bad.

[Jcong]

Please help me as my son’s exam is tomorrow. I still cannot solve the problem here.


Ken had three times as many apples as papays, After selling 160 apples and 25 papayas, he had twice as many papayas as apples left. How many fruits did he have at first?

[corneyAmber]

http://i54.tinypic.com/2cqy4qt.jpg\">

[Jcong]

Please help me with another question that I cannot figure out:Please help me I don’t know where to find the answer!! Help!!


Alan, Bill and Carl started $372. After Alan spent 2/5 of his share, Bill spent 1/2 of his share and Carl spent 1/3 of his share, the boys found that they have the same amount of money left.

1. What is the ratio of Alan’s share to Bill’s share to Carl’s share?
(express your answer in the simplest form)

2. How much did they spend altogether?

[SoWoW]

Help needed for the following questions:


Q1 : Tom and Jerry each has some money. If Tom spends $90 per day and jerry spends $45 per day, Tom will have $1100 left when Jerry has spent all his money. If Tom spends $45 each day and Jerry spends $90 each day. Tom will have $1700 left when Jerry has spent all his money. How much did Jerry have?

Q2 : Ravi had a total of 204 goldfish and swordtails in the ratio of 9:8. After she gave away an equal number of each type of fish , the number of goldfish and swordtails left was in the ratio of 9:5 respectively. What was the total number of fish that she had given away?


Q3: Aifang, Bala and Cindy shared some sweets. Aifang received 1/11 of the sweets. Bala received 1/4 of the number of sweets Cindy received. When cindy gave away 104 sweets to be shared between Aifang and Bala, they found that all of them had the same number of sweets. How many sweets were there at first?

[tinasen]

Hi ADoc,

I was going through the same problem (3) as below. I couldn't get how the net total remains unchanged as either the white or dark chocolates get eaten up. Would it mean -3 from total in either case. I also checked the another problem in couple of pages back about the red and blue marbles. In the marble problem case, I could understand as it's a mere replacement. Can pls help me to clarify?

- Thanks.
Tina

ADoc:

Apphia:

1) Mr Indra is 48 yrs old and his son is 14 yrs old now. How many years later will Mr Indra be twice the age of his son?

2) A pet shop owner bought some cans of dog food. He divided the dog food equally among his dogs. If he bought 7 cans for each dog, he would have bought 4 extra cans. If he bought 11 cans for each dog, he would need 28 more cans.
a)How many dogs were there in the pet shop?
b) How many cans did the owner buy?

3) Mr Chen sold golf balls in packs of 6. The selling price of each pack of golf balls was $22. He sold 60% of his golf balls at $22 per pack and the rest at a discount of 50%. He collected $2640 from the sale of all the golf balls. How many golf balls did he sell altogether?

4) Siti has some dark chocolates and white chocolates in a container. If she eats 3 dark chocolates, the ratio of the number of dark chocolates to the number of white chocolates will become 5:4. If she eats 3 white chocolates, the ratio of the number of dark chocolates will then be 7:5. What is the original number of dark chocolates and white chocolates in the container?

5)Given that 12:28 = ? : 21, what is the number in the ?

Sorry for asking so many questions.

Thank you so much.

Hi! Quick answers..pls let me know if you require the models (some questions do not) for clarity. I love drawing them anway but guess it's an overkill sometimes. cheers!

(1) Key Concept: the difference between the ages remains constant (hence increase the ratio by some multiple so that the difference between the ratio units are the same as before)

now
Indra : Son = 48 : 14 (difference = 48-14 = 34)
years later
Indra : Son = 2 : 1 (difference = 2-1 = 1, but we need 34)
= (2 x 34) : (1 x 34) = 68 : 34
ans = 68 - 48 = 20 yrs' time or 34 - 14 = 20

(2) there's some problem with the wording of the question but here's my suggested solution anyway based on the typical mode of such questions.

number of dogs = D units
7 cans, 4 extra --> total cans he bought = 7D + 4
11 cans, 28 short --> total cans he bought = 11D - 28 [minus 28 because 11D is 28 more than the total number of cans he bought]

since no change in cans, therefore 7D + 4 = 11D - 28
--> 4D = 32, therefore D = 8
Ans = 8 dogs
He bought 8 x 7 + 4 = 60 cans

(3) key concept: converting ratio units to ratio in terms of worth (i.e. $)

number of $22 packs sold : number of 50% ($11) packs = 6 : 4 = 3 : 2 (must be able to convert between equivalent ratio --> fraction --> percentage)

ratio of sales revenue ($) from $22 pack : ratio of sales revenue ($) from $11 pack = (3 x 22) : (2 x 11) = 3 : 1 (4 Units)

4Units --> $2640
1Unit --> $2640/4 = $660, therefore 3Units --> $660 x 3 = $1980
number of $22 packs sold = 1980/22 = 90 number of $11 packs sold = 660/11 = 60
ans = total number of packs x 6 balls = (90 + 60) x 6 = 150 x 6 = 900 [rem to check that $22 packs = 60% of total number of packs in case you arrive at the wrong answer, since there are a number of combinations of $22 & $11 packs that will give $2640]

(4) shall leave you to solve on your own. refer to a couple of pages back.
key concept: the number of units remains unchanged after subtracting either 3 white or 3 dark chocolates (take note if question changes to subtraction of different numbers)

(5) key concept: equivalent ratios (factors & multiples)
12 : 28 = ? : 21

12 : 28 = 3 : 7 = (3 x 3) : (7 x 3) = 9 : 21
ans: ? = 9

alternative if you are familiar with ratios & fractions (including percentages) already ---> (? / 12) = (21 / 28) ....