Q&A - PSLE Math

[Bunny27]

MathIzzzFun:

Bunny27:

Hi, someone pls help on this question:

1. Myra wrote 4 numbers.
The average of the second and fourth number is k. The sum of first and fourth numbers is 40. The sum of second and third numbers is 30.
a) Express the sum of first and third numbers in terms of k.
b) If k=16, find the average of first and third numbers.

TIA

hi

1st + 2nd + 3rd + 4th = 40 + 30 = 70
2nd + 4th = 2k
So, 1st + 3rd = 70 - 2k

If k=16,
1st + 3rd = 70- 2x16= 38
average of 1st & 3rd = 19

cheers.

Thank you

[MathIzzzFun]

Bunny27:

MathIzzzFun:

Hi, someone pls help on this question:

1. Myra wrote 4 numbers.
The average of the second and fourth number is k. The sum of first and fourth numbers is 40. The sum of second and third numbers is 30.
a) Express the sum of first and third numbers in terms of k.
b) If k=16, find the average of first and third numbers.

TIA
hi

1st + 2nd + 3rd + 4th = 40 + 30 = 70
2nd + 4th = 2k
So, 1st + 3rd = 70 - 2k

If k=16,
1st + 3rd = 70- 2x16= 38
average of 1st & 3rd = 19

cheers.

Thank you

avec plaisir

cheers.

[Bunny27]

Bunny27:

MathIzzzFun:

[quote=\"Bunny27\"]

Hi, someone pls help on this question:

1. Myra wrote 4 numbers.
The average of the second and fourth number is k. The sum of first and fourth numbers is 40. The sum of second and third numbers is 30.
a) Express the sum of first and third numbers in terms of k.
b) If k=16, find the average of first and third numbers.

TIA

hi

1st + 2nd + 3rd + 4th = 40 + 30 = 70
2nd + 4th = 2k
So, 1st + 3rd = 70 - 2k

If k=16,
1st + 3rd = 70- 2x16= 38
average of 1st & 3rd = 19

cheers.

Thank you :)[/quote]
Hi, I need help on one more question:
1. In 2009, the ratio of the number of boys to the number of girls in a school was 7:9. In 2010, 162 children joined the school. The new ratio of the number of boys to the number of girls was 7:8.
Find the number of girls who joined the school if there were 546 boys in 2010.

Thanks again

[speedmaths.012624com]

Bunny27:

Hi, I need help on one more question:
1. In 2009, the ratio of the number of boys to the number of girls in a school was 7:9. In 2010, 162 children joined the school. The new ratio of the number of boys to the number of girls was 7:8.
Find the number of girls who joined the school if there were 546 boys in 2010.

Thanks again

Hi,

There were 546 boys in 2010.
There were 546 x 8 / 7 = 624 girls in 2010.
Total = 1170 children in 2010.

There were 1170 - 162 = 1008 children in 2009.

There were 1008 x 9 / 16 = 567 girls in 2009.

Can you work from here?

Cheers


speedmaths.com

.

[thinkgmama]

Hi, please kindly help with this question.


Cherie had 3 times as much money as Jolene. After Cherie spent $40 and Jolene spent $8, Jolene had 3 times as much money as Cherie. How much money did Cherie have at first?

[tianzhu]

thinkgmama:

Hi, please kindly help with this question.


Cherie had 3 times as much money as Jolene. After Cherie spent $40 and Jolene spent $8, Jolene had 3 times as much money as Cherie. How much money did Cherie have at first?

Hi

You may use “Units and parts”

At first
Cherie:Jolene ------ 3 units: 1 unit

Change
Cherie:Jolene ------ -40:-8

In the end
Cherie:Jolene ------ 1 part:3 parts

3 units – 40 ------ 1 part
(x3)
9 units – 120 ------ 3 parts

1 unit - 8 ------ 3 parts

Equalising the parts or cross multiply.

9 units – 120 ------ 1 unit – 8
8 units ------- 112
1 unit ------ 8

Cherie@first ------- 3*14 -------42

Best wishes

[brastilava]

Hi, can someone help to solve this question:


Leon bought some terrapins and guppies for a total of $96. He bought 3 times as many guppies as terrapins. He paid $30 more for the terrapins than for the guppies. Each terrapin cost $10.40 more than each guppy.
(a) How many terrapins did he buy?
(b) What was the cost of each guppy?

[tianzhu]

brastilava:

Hi, can someone help to solve this question:


Leon bought some terrapins and guppies for a total of $96. He bought 3 times as many guppies as terrapins. He paid $30 more for the terrapins than for the guppies. Each terrapin cost $10.40 more than each guppy.
(a) How many terrapins did he buy?
(b) What was the cost of each guppy?

Hi

Terrapins ------ 63
Guppies ------- 33

33/3 ------ 11

1 unit of guppies ------ 11

63 – 11 ------ 52

1 unit of terrapins costs 52 more than 1 unit of guppies.

52/10.4 ------ 5 (number of terrapins)

Number of guppies ------- 3*5 -------15

Cost of 1 guppies -------- 33/15 ------ 2.20

Best wishes

[brastilava]

tianzhu:

brastilava:

Hi, can someone help to solve this question:


Leon bought some terrapins and guppies for a total of $96. He bought 3 times as many guppies as terrapins. He paid $30 more for the terrapins than for the guppies. Each terrapin cost $10.40 more than each guppy.
(a) How many terrapins did he buy?
(b) What was the cost of each guppy?

Hi

Terrapins ------ 63
Guppies ------- 33

33/3 ------ 11

1 unit of guppies ------ 11

63 – 11 ------ 52

1 unit of terrapins costs 52 more than 1 unit of guppies.

52/10.4 ------ 5 (number of terrapins)

Number of guppies ------- 3*5 -------15

Cost of 1 guppies -------- 33/15 ------ 2.20

Best wishes

Thank-you so much

[Chan09]

need some guidance on this?

a) Jack travelled from City A to City B at an average speed of 60 km/h.
He returned from City B to City A at an average speed of 100 km/h.
What was Jack’s average speed for the whole journey?

tks