Q&A - P4 Math

[MathIzzzFun]

milo-cupcake:

Hello , please help me this question with assumption method.


At a sale, the erasers were priced at 4 for $2 while the markers were priced at 2 for $3 . Miss Macy bought a total of 26 eraser and markers for $23 . Find the number of erasers that Miss Macy bought.

Thank you in advanced. :thankyou:

1 eraser -> $0. 50
1 marker -> $1. 50
price difference -> $ 1. 00

Assume Macy bought all markers, total amount paid = 26 x $1. 50 = $39
amount overpaid for erasers = $ 39 - $ 23 = $16
number of erasers bought = $16 ÷ $1 = 16
number of markers bought = 10

cheers

[peapot]

BigDevil:

snowball:

:thankyou: :please:
for this type of questions, how do we see (beginning) how many units to draw in the model? eg, for the above qn, 6units to draw for the men :?

You will realise what model to draw if you can think of this question in fractions.

At first, there were twice the number of men as women. That's the same as saying number of women is 1/2 of men.

Likewise, at the end, number of women is 1/3 of men.

Changing to same denominator, you get 3/6 at first, and 2/6 at the end.
You can then proceed to solve the problem with fractions (1/6 = 12),
or draw the model with 6 units for men.

You can also draw the following alternate model for this question without realising you need to draw 6 units for men:
http://i48.tinypic.com/iznno9.jpg\">

Big devil!! You are the first person who actually enlighten me. Very clear explanation!! I finally understand how to draw the model. Like many parents I have a problem wondering how many boxes to draw. No one told me to think in fraction, not even my dd's tutor! Thanks!!!
Btw, can we always use fraction to draw box models for all problem sum that has twice as many, 4 times more etc? Can we also find out man first instead of starting to find woman first?

[peapot]

HAPPYH:

I need help to understand the following (Pardon me if this is a very basic question; Obviously I am not sure)


Estimate the answer

535 + 320 = ?

567+341 = ?

They never say round off to the nearest tens or hundreds. Then how do we know for sure?

For eg:
535 + 320 = 540 + 320 = 860
535 + 320 = 500 + 300 = 800

Which one is correct? And why?

Thank you in advance.

I would think 860 should be the ans. we are asked to estimate the ans so the ans must be the closest to the real ans. this means u should round to nearest 10s.

[milo-cupcake]

Hi , please help me this question with assumption method.


Doreen paid $25 for 35 pens and pencils altogether.The pen were sold at $2 each and the pencils were sold at 3 for $1. How many pencil did she buy?

Thank you

[milo-cupcake]

quekcc:

Similar method that MathIzzzFun had presented.


1 pen -> $2. 00
3 pencils -> $1. 00
Since you have to buy pencils in multiple of 3, we work out the difference of 3 pen and 3 pencils -> $5.00

Assume Doreen bought all pens, total amount paid = 35 x $2. 00 = $70
amount overpaid for pencils = $ 70 - $ 25= $45
number of set (i.e. 3 pencils) of pencils bought = $45 ÷ $5 = 9
number of pencils bought = 3 x 9 = 27

Thanks quekcc :thankyou:

[jacsplace]

Are there any websites – other than this forum of course – where maths questions are posted up and explanations provided on how to solve them?

[Jamesbond]

Sudden confusion.....Pl clear my doubts...

Q1)
What is the best estimate of the value 4.59*101?
1)400
2)450
3)460
4)500

Q2)A rectangular garden measures 2.25m by 3m. What is the area of the garden? Round off your answer to 1decimal place.
Is the answer 6.5 or 6.8 for this.... :scratchhead:

[Jamesbond]

quekcc:

Q1, best estimate is 460 = 4.6 x 100


Q2, evaluate the answer and then round-off to 1 decimal, so should be 6.8.

Regarding Q1, Why cant we change the decimal into whole numbers? So I opted for 4) 500. Pl clear my doubt....

[Poppet]

Mr Lim received a year-end bouns of $4135.Mrs Lim received a year-end bouns of $6940.They each spent an equal amount of money on Christmas gifts.Mrs Lim was left with 4 times as much money as Mr Lim.How much money did they spent in all?



Can anyone help to solve this question? :thankyou:

[Pen88n]

Poppet:

Mr Lim received a year-end bouns of $4135.Mrs Lim received a year-end bouns of $6940.They each spent an equal amount of money on Christmas gifts.Mrs Lim was left with 4 times as much money as Mr Lim.How much money did they spent in all?



Can anyone help to solve this question? :thankyou:

Before:
Mr Lim: [$4135]
Mrs Lim: $6940 = [$4135] + [$2805]

After:
Mr Lim: [1u]
Mrs Lim: [1u][1u][1u][1u]

Since they spent same amount, looking at the before state, the [$4135] of both parties should be reduced to [1u] after the spending.

Thus, from Mrs Lim side:
3u = $2805
u = $935

Spending = ($4135 - $935) x 2 = $6400