Q&A - P3 Math

[MathIzzzFun]

bookwormkids:

P3 Maths


A watch costs $100 more than a pen. The watch also costs twice as much as a ring. The total cost of the 3 items is $250. Find the cost of the pen.

Thanks!

Hi

using MD ...

http://i56.tinypic.com/2a0gaww.jpg\">

cheers.

[bookwormkids]

Hi jedamum!

Thanks for your solution. Your solution is perfectly acceptable so long as the kid understand it... I was stucked at the pen and the watch part. Thanks for your solution, now I know where goes wrong.

[bookwormkids]

Hi MathIzzzFun!


With your model, I think I could clear my kid's query! Thanks for your help!

[aps]

Hi all


Please help me with this question. I need the model approach. Thanks.

John bought some books which cost an average of $26. Two of the books cost $46 and $34 respectively. If the average cost of the remaining books was $22, find the total number of books he bought.

[MathIzzzFun]

aps:

Hi all


Please help me with this question. I need the model approach. Thanks.

John bought some books which cost an average of $26. Two of the books cost $46 and $34 respectively. If the average cost of the remaining books was $22, find the total number of books he bought.

Hi

There is a similar question which was discussed at this thread - http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=27&t=6373&hilit=overall+average+will+be+85&start=3630

cheers.

[MathIzzzFun]

bookwormkids:

Hi MathIzzzFun!


With your model, I think I could clear my kid's query! Thanks for your help!

u r welcome.

cheers.

[whywhy]

Tin A contains some 20-cents coins and Tin B contains some 50-cents coins.

There are 9 more coins in Tin A than in Tin B.
The amount of money in Tin A is $2.70 less than that in Tin B.
How many 50-cents coins are there in Tin B ?

Is guess and check the only method to solve this Question???

[tianzhu]

whywhy:

Tin A contains some 20-cents coins and Tin B contains some 50-cents coins.

There are 9 more coins in Tin A than in Tin B.
The amount of money in Tin A is $2.70 less than that in Tin B.
How many 50-cents coins are there in Tin B ?

Is guess and check the only method to solve this Question???

Hi

Suppose or pretend that you remove 9 20 cents coins from Tin A.

9*20 ---- 180

Now Tin A has (270+180) or 450 cents less than Tin B

Difference in value between a 50 cents coin and 20 cents coin ------ 30 cents.

450/30 ------ 15

There are 15 50 cents coins in Tin B.

Best wishes

[pixiedust]

Is this P4/P5 question ?


…num of coins…*…value…Total amt of money
Tin A…U+9…20cents…20U+180
Tin B…U…50cents…50U
(…for alignment purpose)

50U = 20U + 180 + 270 = 20U + 450
30U = 450
U=15

Ans: There are 15 50-cents coins in Tin B.

---------------------------------------------------
check :
Tin B: 15 coins -> 15 x 50cents = $7.50
Tin A: 24 coins -> 24 x 20cents = $4.80
$7.50-$4.80=$2.70, checked

[pixiedust]

tianzh’s method is faster and more elegant !