Q&A - P4 Math

[tianzhu]

chloecube:

What is the sum of the first 30 even numbers?

2+4+6+8......+56+58+60=

I know there shld a a formula to solve such question.
Can anyone help?

Hi

2+4+6+8......+56+58+60 = 2(1+2+3+ --------- 30)

I think students are familiar with calculating the sum of consecutive numbers.

(1+2+3+ --------- 30) = 465

2*465 = 930

Another way to look at it, there are 15 pairs of 62.

2 + 60 = 62
4 + 58 = 62

15*62 = 930

Best wishes

[Nebbermind]

Another similar way is…Because (2 + 58), (4 + 56)… makes a nice number such as 60, there will be 14 such pairs in this series, with 30 & 60 being the odd ones without a partner.


Therefore (14*60) + 30 + 60.

The reason for choosing this is because its easier to work with numbers which r multiples of 10. May not work for all qns though.

[Champion]

Hi, need help with the following questions; :thankyou:


1) The sum of 3 numbers is 350. The difference between the first number and the second number is 25. The difference between the second and the third number is 36. What is the first number if the first number is the smallest and the third number id the largest?

2) Mrs. Kee baked 3 cakes and shared them equally among her 4 children. How much cake did 3 of her children received? Express your answer in fraction in its simplest form.

[PiggyLalala]

Champion:

Hi, need help with the following questions; :thankyou:


1) The sum of 3 numbers is 350. The difference between the first number and the second number is 25. The difference between the second and the third number is 36. What is the first number if the first number is the smallest and the third number id the largest?

2) Mrs. Kee baked 3 cakes and shared them equally among her 4 children. How much cake did 3 of her children received? Express your answer in fraction in its simplest form.

First =second- 25
Third = second +36
First + second + third = 350
Second -25 +second +second + 36 = 350
3x second =350 -11
3xsecond = 339
Second = 339/3= 113
First = 113-25 = 88
Third =113 +36= 149

Second question: 3/4x3=9/4 =2 1/4

[24hr-mum]

how to do this and how to draw the model?


cameron and niki had a total of 136 guppies at first.
After cameron had bought another 14 guppies and niki gave away 40 guppies, both
have the same number of guppies left. how many guppies did cameron have at first?

i cant understand why it is not 136-14-14-40 for the first step.

[Champion]

PiggyLalala:

Champion:

Hi, need help with the following questions; :thankyou:


1) The sum of 3 numbers is 350. The difference between the first number and the second number is 25. The difference between the second and the third number is 36. What is the first number if the first number is the smallest and the third number id the largest?

2) Mrs. Kee baked 3 cakes and shared them equally among her 4 children. How much cake did 3 of her children received? Express your answer in fraction in its simplest form.

First =second- 25
Third = second +36
First + second + third = 350
Second -25 +second +second + 36 = 350
3x second =350 -11
3xsecond = 339
Second = 339/3= 113
First = 113-25 = 88
Third =113 +36= 149

Second question: 3/4x3=9/4 =2 1/4

:thankyou: :thankyou: PiggyLalala for the explanation; appreciates much

[tianzhu]

Hi


Hope this helps.

Best wishes.

http://farm6.staticflickr.com/5234/6936350842_d90e22fbfb_z.jpg\">

[chloecube]

tianzhu:

chloecube:

What is the sum of the first 30 even numbers?

2+4+6+8......+56+58+60=

I know there shld a a formula to solve such question.
Can anyone help?

Hi

2+4+6+8......+56+58+60 = 2(1+2+3+ --------- 30)

I think students are familiar with calculating the sum of consecutive numbers.

(1+2+3+ --------- 30) = 465

2*465 = 930

Another way to look at it, there are 15 pairs of 62.

2 + 60 = 62
4 + 58 = 62

15*62 = 930

Best wishes

noted, thks Tianzhu

[24hr-mum]

tianzhu:

Hi


Hope this helps.

Best wishes.

http://farm6.staticflickr.com/5234/6936350842_d90e22fbfb_z.jpg\">

thanks tianzhu for the beautiful illustration.
so i guess the ans key is wrong. it says 136-40-14 = 82
then 82/2=41.

[Nebbermind]

chloecube:

What is the sum of the first 30 even numbers?

2+4+6+8......+56+58+60=

I know there shld a a formula to solve such question.
Can anyone help?

I was told this kind of qns not in the p4 syllabus...maybe can find in MO or some enrichment schools programme. Is it true?