Q&A - P5 Math

[AtoZ]

MathIzzzFun, I have pm you. Thanks!

[sokk]

Hi,


Need a help for this question from My Pals Are Here Maths Enrichment P5A .

At a Science competition, 25 problems were given. Each correct answer earned 4 points, and 2 points were deducted for each incorrect answer. Liang Hong answered all but one of the problems receiving a score of 66. How many correct answers did she have?


Thanks !

[MathIzzzFun]

sokk:

Hi,


Need a help for this question from My Pals Are Here Maths Enrichment P5A .

At a Science competition, 25 problems were given. Each correct answer earned 4 points, and 2 points were deducted for each incorrect answer. Liang Hong answered all but one of the problems receiving a score of 66. How many correct answers did she have?


Thanks !

You can use Guess & Check or supposition or the area model method...

here's a similar one using area model (which is supposition method in model)- http://www.flickr.com/photos/62167097@N02/7634466300/in/photostream

for your question, need to tweak a little --> total number of questions answered is 24.

all questions answered correctly --> 24 x 4 = 96
96 - 66 = 30 (points lost for questions answered wrongly)
questions answered wrongly --> 30 / (4+2) = 5
questions answered correctly --> 24 - 5 = 19

cheers.

[sokk]

Hi MathIzzzFun,


Thanks for the solution!


cheers

[Jamesbond]

Mr Wang changed a $1000 note into 42 and $10 notes. The total value of the $10 notes was 9 times the value of the $2 notes. He decided to give 2/5 of his $10 notes and 2/5 of his $2 notes to charity. He then exchanged the remaining of his money for $5 notes. How many notes did he have in the end?


My ds could not solve it…The ans is 120. Pl help n explain it…Thx.

[MathIzzzFun]

[quote="Jamesbond"]Mr Wang changed a $1000 note into 42 and $10 notes. The total value of the $10 notes was 9 times the value of the $2 notes. He decided to give 2/5 of his $10 notes and 2/5 of his $2 notes to charity. He then exchanged the remaining of his money for $5 notes. How many notes did he have in the end?


My ds could not solve it…The ans is 120. Pl help n explain it…Thx.[/quote


Spent 2/5 of $10 notes n 2/5 of $2 notes
= Spent 2/5 of money
so, 3/5 money left -> 3/5 x $1000 = $ 600

number of $5 notes = $600 / $5 = 120

cheers.

[Jamesbond]

[quote="MathIzzzFun"][quote="Jamesbond"]Mr Wang changed a $1000 note into 42 and $10 notes. The total value of the $10 notes was 9 times the value of the $2 notes. He decided to give 2/5 of his $10 notes and 2/5 of his $2 notes to charity. He then exchanged the remaining of his money for $5 notes. How many notes did he have in the end?


My ds could not solve it…The ans is 120. Pl help n explain it…Thx.[/quote


Spent 2/5 of $10 notes n 2/5 of $2 notes
= Spent 2/5 of money
so, 3/5 money left -> 3/5 x $1000 = $ 600

number of $5 notes = $600 / $5 = 120

Thx mathizzfun…pl help me in another sum…

Tan current age is 1/4 of Ronald’s. In 24 years time Ronald’s age will be 14 years less than twice Marks age. what is Ronald’s age now? Thx.

[MathIzzzFun]

Jamesbond:

MathIzzzFun:

[quote=\"Jamesbond\"]Mr Wang changed a $1000 note into 42 and $10 notes. The total value of the $10 notes was 9 times the value of the $2 notes. He decided to give 2/5 of his $10 notes and 2/5 of his $2 notes to charity. He then exchanged the remaining of his money for $5 notes. How many notes did he have in the end?


My ds could not solve it....The ans is 120. Pl help n explain it.....Thx.[/quote


Spent 2/5 of $10 notes n 2/5 of $2 notes
= Spent 2/5 of money
so, 3/5 money left -> 3/5 x $1000 = $ 600

number of $5 notes = $600 / $5 = 120

Thx mathizzfun.....pl help me in another sum...

Tan current age is 1/4 of Ronald's. In 24 years time Ronald's age will be 14 years less than twice Marks age. what is Ronald's age now? Thx.

[/quote]...is Tan supposed be Mark or the name is supposed to be Mark Tan ?

cheers.

[Jamesbond]

Oh so sorry mathizzfun.....typo error.. :slapshead: It is tan only....loads n loads of homework in beginning of P5 itself am struggling to help my ds in his work.....


Tans current age is 1/4 of Ronald's. In 24 years time Ronald's age will be 14 years less than twice tans age. What is Ronald's age now?

TIA....

[MathIzzzFun]

Jamesbond:

Oh so sorry mathizzfun.....typo error.. :slapshead: It is tan only....loads n loads of homework in beginning of P5 itself am struggling to help my ds in his work.....


Tans current age is 1/4 of Ronald's. In 24 years time Ronald's age will be 14 years less than twice tans age. What is Ronald's age now?

TIA....

http://i46.tinypic.com/5w9xch.png\">

cheers.