Tutor MathsGuru: Ask me for your burning Maths questions!

[SoWoW]

Hi,the question is :

A small van can seat at most 8 people, including the driver, at one time. What is the least number of trips made by the driver , if he has to transport all 157 people from Town A to Town B.
The answer is 23.
My question is why not 46 trips when the driver has to make a trip back from Town B to Town A to pick up another batch of people.
Please help.

[she0407]

Hi, need help for the following Qs:


1. The average mass of a group of pupils was 28 kg. When Mr Lim measured and recorded the mass of these pupils, he wrongly recorded one pupil's weight as 53 kg when it should be 35kg. As a result, the average weight of the pupils was recorded as 29kg. how many pupils were there?

2.The ratio of Sammy's age to Peter's age is 10:7. In 8 years' time, the ratio will become 4:3. What is Sammy's age now?

3. In the number line below, A represents 1/5, C represents 1/3 and AB = BC. What is the fraction represented by B?



:thankyou:

[MathIzzzFun]

she0407:

Hi, need help for the following Qs:


1. The average mass of a group of pupils was 28 kg. When Mr Lim measured and recorded the mass of these pupils, he wrongly recorded one pupil's weight as 53 kg when it should be 35kg. As a result, the average weight of the pupils was recorded as 29kg. how many pupils were there?

2.The ratio of Sammy's age to Peter's age is 10:7. In 8 years' time, the ratio will become 4:3. What is Sammy's age now?

3. In the number line below, A represents 1/5, C represents 1/3 and AB = BC. What is the fraction represented by B?



:thankyou:

Hi

1. (53-35)/(29-28)=18/1 = 18 pupils -> The increase in the average weight (+1) is due to the increase in the wrongly recorded weight (53-35)

2. Age difference will always remain the same.
at first, Sammy : Peter = 10u : 7u (difference 3u)
8 years' time, Sammy : Peter = 4:3 = 12u:9u (difference 3u)

so 12u-10u (or 9u-7u) =8, 1u = 4
Sammy's age now = 10u = 40

3. B = (A+C)/2 = (1/5+1/3)/2 = 4/15

Alternatively, A= 1/5 = 3/15, C=1/3 = 5/15, C-A = 2/15 = AC, AB =1/2 AC =1/15
B= A + 1/15 = 3/15 + 1/15 = 4/15

cheers.

[pokemon97]

can somebody help me solve this question?


The numbers of books Mrs Tee had is 4/5 the number of books Mrs Chua had. Mrs Tang had 60% fewer books than Mrs Tee. Mrs Tee and Mrs Chua gaveMrs Tang some books in the ratio of 3:2. As a result, Mrs Tand had 1 1/2 times as many books as before. Given that Mrs Chua had 261 books more than Mrs Tee in the end, how many books did Mrs Tee give to Mrs Tang?


Thanks

[Herbie]

can someone help to solve this burning maths qn?

The intensity of illumination, l lumen/m2, at a point on a screen is inversely proportional to the square of the dstance, d metre , ofthe light source fromthe point. Given that d=25m when l =0.8 lumen/m 2, find
A. l when d=1.25, my ans is 3.2 lumens/m2
B. d, when l=0.05 lumens/m2. My ans is 10

Are both answers correct?

[MathIzzzFun]

Herbie:

can someone help to solve this burning maths qn?

The intensity of illumination, l lumen/m2, at a point on a screen is inversely proportional to the square of the dstance, d metre , ofthe light source fromthe point. Given that d=25m when l =0.8 lumen/m 2, find
A. l when d=1.25, my ans is 3.2 lumens/m2
B. d, when l=0.05 lumens/m2. My ans is 10

Are both answers correct?

Hi

l is inversely proportional to square of the distance
so, l = k/d^2, where k is a constant.

at d= 25m, l = 0.8 = k/625, k = 500

now use l = 500/d^2 to find l and d for A and B, you should get
A. l = 320 lumens/square m
B. d = 100m

cheers.

[MathIzzzFun]

pokemon97:

can somebody help me solve this question?


The numbers of books Mrs Tee had is 4/5 the number of books Mrs Chua had. Mrs Tang had 60% fewer books than Mrs Tee. Mrs Tee and Mrs Chua gaveMrs Tang some books in the ratio of 3:2. As a result, Mrs Tand had 1 1/2 times as many books as before. Given that Mrs Chua had 261 books more than Mrs Tee in the end, how many books did Mrs Tee give to Mrs Tang?


Thanks

Hi

Tee : Chua = 4:5
Tang : Tee = 4:10 = 2:5
So, Tang : Tee : Chua = 8u: 20u : 25u

In the end, Tang had 1.5 times as many books
so, total number of books given by Tee and Chua = 0.5 x 8u = 4u

Tee gave 3/5 x 4u = 2.4u
Chua gave 2/5 x 4u = 1.6u

In the end,
Tee had 20u - 2.4u = 17.6u
Chua had 25u - 1.6u = 23.4u

Chua had 261 books more than Tee in the end,
23.4u - 17.6u = 261
5.8u = 261, 1u = 45

Mrs Tee gave 2.4u = 2.4 x 45 = 108 books to Mrs Chua

cheers.

[Herbie]

thanks mathsizzfun, sorry, i just dscovered i hv a topo error, d should be= 2.5m and not 25m.


Thanks for working it out for me! Many thanks!!

[Chan09]

Dear all, need some help on this:

B and C had a total of $1475 at first. After B spent 4/7 of his money and C spent $145. C found that the amt of money he had left was 5/6 of what B had left. How much more money had B than C at first?
Tks
And: $485

[MathIzzzFun]

Chan09:

Dear all, need some help on this:

B and C had a total of $1475 at first. After B spent 4/7 of his money and C spent $145. C found that the amt of money he had left was 5/6 of what B had left. How much more money had B than C at first?
Tks
And: $485

Hi

After B spent 4/7 of his money (ie 3/7 left) and C spent $145,
B: C = 6u : 5u
B's total = 7/3 x 6u = 14u
C's total = 5u + $145
B & C had total of $ 1475 at first --> 14u + 5u + $145 = $1475,
19u = $1330, 1u = $70

B-C = 14u - 5u - $ 145 = 9u - $145 = $630 - $ 145 = $485
B had $485 more than C at first.

cheers.