Q&A - P5 Math

[MathIzzzFun]

chloecube:

Jane bought some slices of cheesecake and mango cake.she spend $60 and $40 on the cheesecake and mango cake respectively. each slice of mango cake cost $2 more than each slice of the cheesecake.she bought twice as many cheesecake as mango cakes. find the cost of each slice of cheesecake.

First, find the amount spent on same number of cheesecakes and mango cakes ie 1 unit of cheesecakes and 1 unit of mango cakes OR 2 units cheesecakes and 2 units of mango cakes

1 unit of cheesecakes --> $60/2 = $30
1 unit of mango cakes --> $40
$40 - $30 = $10
Number of slices of cakes in 1 unit --> $10 / $2 = 5

cost of 1 slice of cheesecake = $ 30/5 = $6

cheers.

[chloecube]

MathIzzzFun:

chloecube:

Jane bought some slices of cheesecake and mango cake.she spend $60 and $40 on the cheesecake and mango cake respectively. each slice of mango cake cost $2 more than each slice of the cheesecake.she bought twice as many cheesecake as mango cakes. find the cost of each slice of cheesecake.

First, find the amount spent on same number of cheesecakes and mango cakes ie 1 unit of cheesecakes and 1 unit of mango cakes OR 2 units cheesecakes and 2 units of mango cakes

1 unit of cheesecakes --> $60/2 = $30
1 unit of mango cakes --> $40
$40 - $30 = $10
Number of slices of cakes in 1 unit --> $10 / $2 = 5

cost of 1 slice of cheesecake = $ 30/5 = $6

cheers.

thks for getting back.

i do not quite under this part,
\"Number of slices of cakes in 1 unit --> $10 / $2 = 5\"

i understand $10 is the difference between the 2 cakes if equal nos of cakes are bought, and $2 is the price difference.
so what is 5?

[MathIzzzFun]

chloecube:

MathIzzzFun:

[quote=\"chloecube\"]Jane bought some slices of cheesecake and mango cake.she spend $60 and $40 on the cheesecake and mango cake respectively. each slice of mango cake cost $2 more than each slice of the cheesecake.she bought twice as many cheesecake as mango cakes. find the cost of each slice of cheesecake.

First, find the amount spent on same number of cheesecakes and mango cakes ie 1 unit of cheesecakes and 1 unit of mango cakes OR 2 units cheesecakes and 2 units of mango cakes

1 unit of cheesecakes --> $60/2 = $30
1 unit of mango cakes --> $40
$40 - $30 = $10
Number of slices of cakes in 1 unit --> $10 / $2 = 5

cost of 1 slice of cheesecake = $ 30/5 = $6

cheers.

thks for getting back.

i do not quite under this part,
\"Number of slices of cakes in 1 unit --> $10 / $2 = 5\"

i understand $10 is the difference between the 2 cakes if equal nos of cakes are bought, and $2 is the price difference.
so what is 5?[/quote]do not confuse with slices and a whole cake... the question states Jane bought some slices of cakes...in the working, 1 unit represents number of slices of cakes...

cost difference of 1 slice of cheesecake and 1 slice of mango cake --> $2
so, if the cost difference is $4, then there are 2 slices of each,

The difference in cost is $10 --> 5 slices of each (1 unit)

total number of slices of cheesecakes bought = 10 --> $60, $6/slice
total number of slices of mango cakes bought = 5 --> $ 40, $8/slice

cheers.

[cmm]

tianzhu:

Hi

Please study Jamesbond’s question on pg 167 and pg170.

http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=68&t=25129&start=1670

http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=68&t=25129&start=1690

The answers are 190 white triangles and pattern 130.

Best wishes

Hi tianzhu, regarding the above question, can explain how to get n x (n+1)/2? Is it same as the question 1 + 2 + 3 + 4....... + n? Then are we assuming that n is an even number cos if n is odd, the we need to add the number in the middle of the set to the formula.

Also, may I know how to solve n + n x n = 17030? Is it simply square root 17030 and just take the whole number to be the answer (130)? Rather difficult to P5 who needs absolutes as answers.

Thank you!

[imacsg]

CA1 Nan Hua Q16


Pls help to solve the below question. Can you advise the Assume method instead of Guess and check method. Thanks.

A total of 360 teachers and pupils participated in tree planting. Each teacher planted 3 trees and each group of 3 pupils planted 2 trees. if 520 trees were planted, how many pupils were there?

Assume all are teachers

360 x 3 = 1080
1080 - 520 = 560
560 / ?

Then I do not know how to do?

[tianzhu]

imacsg:

CA1 Nan Hua Q16


Pls help to solve the below question. Can you advise the Assume method instead of Guess and check method. Thanks.

A total of 360 teachers and pupils participated in tree planting. Each teacher planted 3 trees and each group of 3 pupils planted 2 trees. if 520 trees were planted, how many pupils were there?

Hi

Please go to this link for a similar question.

Best wishes

http://www.kiasuparents.com/kiasu/forum/viewtopic.php&f=69&t=280&p=703702

http://farm8.staticflickr.com/7022/6518324819_548ca9d2dc_z.jpg\">

[MathIzzzFun]

imacsg:

CA1 Nan Hua Q16


Pls help to solve the below question. Can you advise the Assume method instead of Guess and check method. Thanks.

A total of 360 teachers and pupils participated in tree planting. Each teacher planted 3 trees and each group of 3 pupils planted 2 trees. if 520 trees were planted, how many pupils were there?

Assume all are teachers

360 x 3 = 1080
1080 - 520 = 560
560 / ?

Then I do not know how to do?

work out the difference for group of same number of teachers & pupils:
3 teachers --> 9 trees
3 pupils --> 2 trees
difference of 7 trees ie 3 teachers planted 7 more trees than 3 pupils

assume trees planted by all teachers --> 360 x 3 = 1080 trees
1080 - 520 = 560 --> over count of 560 trees planted by pupils
number of groups of 3 pupils = 560 / 7 = 80
Number of pupils --> 80 x 3 = 240
Number of teachers --> 360 - 240 = 120

cheers.

[tianzhu]

cmm:

tianzhu:

Hi

Please study Jamesbond’s question on pg 167 and pg170.

http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=68&t=25129&start=1670

http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=68&t=25129&start=1690

The answers are 190 white triangles and pattern 130.

Best wishes

Hi tianzhu, regarding the above question, can explain how to get n x (n+1)/2? Is it same as the question 1 + 2 + 3 + 4....... + n? Then are we assuming that n is an even number cos if n is odd, the we need to add the number in the middle of the set to the formula.

Also, may I know how to solve n + n x n = 17030? Is it simply square root 17030 and just take the whole number to be the answer (130)? Rather difficult to P5 who needs absolutes as answers.

Thank you!

Hi

The sequence for black triangles in your question is 1,3,6,10 .....

Please refer to the slide and look at the table on pattern number and white squares (1,3,6,10....)

It does not matter whether the pattern number is even or odd, the sequence follows n(n+1)/2.

n(n+1)/2 ------ 8815

Hence, n(n+1) ------- 17030

The multiplication of two consecutive numbers leads to 17030.With the use of calculators in primary maths, it’s not too difficult to arrive at the answer with a bit of guess and check.

Yes, you may also find the square root of 17030 and try to make some adjustment.

Best wishes

[imacsg]

Thanks MathIzzzFun and Tianzhu for your prompt reply.

[chloecube]

okok, i got it, thks for the detailed explaination!