Tutor MathsGuru: Ask me for your burning Maths questions!

[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) ....

[Apphia]

Yes, models will be a great help. It will be easier for me to explain to my daughter.


Warm Rgds, Apphia

[Bunny27]

Hi,

Can someone assist me with this question:

Hi,

Can you help of solve this question?
In the 1st week of a fund raising campaign, class 6a raised 4 times as much as class 6b. In the 2nd week, 6a raised another $240 while 6b raised another $160. Given that 6a raised thrice as much as 6b within these 2 weeks, what was the total amount of money raised by the 2 classes?

Thanks!


:welcome:

Dear Parents,

Are you frustrated/stuck when helping your child solve his/her Maths questions? Are you inclined to use Algebra most of the time? Do you have difficulty trying to use diagrams or other heuristic methods (that Primary School students learn) to solve?

:idea: Post your questions here and see how MathsGuru solve them to the best of her ability. Detailed solutions will be posted back in this thread.

So start asking and watch this space!!

Cheers :celebrate: ,
MathsGuru

P/S (Disclaimer, in case you're wondering...):
Although MathsGuru is a full-time Maths tutor, this thread is meant to be an absolutely free resource for parents (or even children) with no strings attached. Just someone who's passionate about Maths and wanna spread the fun in learning Maths with others. :D[/quote][quote=\"mathsguru\"][b]Original Title: Let MathsGuru Answer Your

[ozora]

got a tricky question: thanks for the help

Adam,Ben, Can and Den had a total of 5856 stickers at first. After 1month, Adam’s stickers is increased by 2/3, Ben’s stickers is decreased by 3/13, Can’s stickers is increased by 153 and Den lost 276 of his stickers. They then had the same number of stickers.
a) how many stickers did Adam have at first?
b) how many stickers did Den have at first?

[vannessa]

Hi I need help on a pri 3 question. Hakim is 26 yrs old. He is 8 yrs older than Rick. How many yrs ago was hakim’s age thrice as Rick?

Thank you[/list]

[ADoc]

LaiHeng:

got a tricky question: thanks for the help

Adam,Ben, Can and Den had a total of 5856 stickers at first. After 1month, Adam's stickers is increased by 2/3, Ben's stickers is decreased by 3/13, Can's stickers is increased by 153 and Den lost 276 of his stickers. They then had the same number of stickers.
a) how many stickers did Adam have at first?
b) how many stickers did Den have at first?

Hi there! Here's my answer for your reference.
cheers! have a great weekend!
http://postimage.org/image/27fpebeuc/

[ADoc]

vannessa:

Hi I need help on a pri 3 question. Hakim is 26 yrs old. He is 8 yrs older than Rick. How many yrs ago was hakim's age thrice as Rick?

Thank you[/list]

Hi! I assume you are or your kid is just about learning models maybe? See if any of the three methods suits your needs. I'll try to be as detailed and clear in my solutions since it's a P3 kid.

Most important concept about this sort of question is that we all aged by the same number of years, months, days (i.e. the difference between any two persons' ages is always constant).

1. work backwards (or guess & check)
26 18
25 17
24 16
23 15
22 14
21 13
20 12
19 11
18 10
17 9
16 8
15 7
14 6
13 5
12 4
therefore ans = 26 - 12 = 14 yrs ago


2. ratio
26 : 18 (now)
difference = 26 - 18 = 8 units

3 : 1 (so many years ago; difference = 2 units)
make the difference in units the same as \"now\"
2 x 4 = 8
therefore

3 : 1 = 3 x 4 : 1 x 4 = 12 : 4
therefore 26 - 12 = 14 yrs ago


3. model
ago

[ ] [ ] [ ] Hakim
[ ] Rick

since age difference does not change, therefore \"so many\" years ago, the difference between Hakim's & Rick's age remains as 8 years.

therefore 3 [ ] - 1 [ ] = 2 [ ] = 8
1 [ ] = 8 divide by 2
= 4

this means Rick was 4 year's old when Hakim was thrice Rick's age.
therefore, present age minus 4 year's old = 18 - 4 = 14 yrs ago

[ozora]

thanks

ADoc:

LaiHeng:

got a tricky question: thanks for the help
Adam,Ben, Can and Den had a total of 5856 stickers at first. After 1month, Adam's stickers is increased by 2/3, Ben's stickers is decreased by 3/13, Can's stickers is increased by 153 and Den lost 276 of his stickers. They then had the same number of stickers.
a) how many stickers did Adam have at first?
b) how many stickers did Den have at first?

Hi there! Here's my answer for your reference.
cheers! have a great weekend!
http://postimage.org/image/27fpebeuc/

[vannessa]

Thank you ADoC

[ADoc]

LaiHeng:

thanks

ADoc:

[quote=\"LaiHeng\"]got a tricky question: thanks for the help
Adam,Ben, Can and Den had a total of 5856 stickers at first. After 1month, Adam's stickers is increased by 2/3, Ben's stickers is decreased by 3/13, Can's stickers is increased by 153 and Den lost 276 of his stickers. They then had the same number of stickers.
a) how many stickers did Adam have at first?
b) how many stickers did Den have at first?

Hi there! Here's my answer for your reference.
cheers! have a great weekend!

[/quote]Hi LaiHeng, you're most welcome!