[Prafull]

I havent studied mathematics for last 6-7 years. There is an exam coming soon where I need to prepare for mathematics. I am trying to solve few problems. These are very simple ones and I used to solve them at school. But many of these problems are without solutions (or wrong/doubtful solutions). So the purpose of this thread is to get some help.

I am posting some problems.Some of these I cant solve, some I take too long to solve and some I find really interesting. If you can solve them it would be great.

Post your results here and kindly explain the solution and tell the fastest procedure (shortcuts or anything) to solve them to me via pm so that there arent any spoilers for others.

Other people can also post their questions if they want. Here are few simple ones to start.

(1). A dishonest shopkeeper deceives by 15% at the time of purchase of the articles and also 15% at the time of the sale.Find out the percentage of profit.

(2). A tank is filled 10% in one hour and 8% of the water is emptied in the next hour. If it is repeated again,find the percentage of tank filled with water.

(3). A contactor took a contract for building 12 kilometre road in 15 days and employed 100 labours on the work.After 9 days he found that only 5 kilometre road had been constructed.How many more labours should be employed to ensure that the work may be completed within the given time?

 

[shadow89]

(1)hmmm I would 100 -(15+15) = 70% but I'm not sure =\, i dunno what means to deceive 15% at the time of purchase =\
(2) is 2% every 2 hours, so 1% every hour (average) so...100 hours to make it to hundred eventhough in hour 101 it would 98% =P
(3) 9days 100labours for 5, to make it 6 days that would mean in 2/3 of the time it took to make 5, so 3/2 X 100 = 150 labours to make it in 6 days (that's just 5km though) so we need 7 which is 5/2 , u would need 1/2 of what u needed to make 5 km but you would need to add it so 100+150+75 = 325 labours to make it in 6 days

 

[ChankastRules]

Shadow89 OoOoO did you read the post... send how you arrived at the answers in PM as to not ruin it for others... well it doesn't matter because some of your answers are wrong anyhow ooo well, haha I guess none cared about that part

 

[_E_]

(ii) 11.04%

at t=0 , tank is getting filled to 10% of it's volume ( initial volume assumed to be = 0). t=1, 8% of the water is getting drained -> 0.1V - 0.08V = 0.02V.
t=2, tank getting filled up again, 10% of the tank volume's water is being added -> (0.02 + 0.1)V = 0.12V. at t=3, 8% of the water present is getting drained, so 0.12 - (0.12*0.08) = 0.1104V =11.04%

Didn't understand the 1st part. As for the 3rd part, I ll think of it when I come back home. You just need an equation to relate distance and labour as a function of time.

Yours,
-Elly

 

[TWave]

HERE ARE THE ANSWERS, DO NOT READ THIS IF YOU WANT TO SOLVE IT BY YOURSEFL
Simple.

1.
100 + 15/100*100 + (15/100*(100 + 15/100*100)) = 132.25%
-> The gain is 32.25%, comparing to the original product (100%)

2.
10 - 8/100*10 + 10 - 8/100*(10 - 8/100*10 + 10)) = 17.664%

3.
100*9 = 5 -> Relation 180:1

X*(15-9) = (12-5)
X*6 = 7 -> X = 7/6 -> X*6/7 = 1
To mantain the Relation. -> 180 = X*6/7 -> 1260 = X*6 -> X = 1260/6 = 210
X = Total needed labors, so -> Y = 210 - 100 = 110 more needed workers

 

[TOY]

The answer to #2 is 11.04%


TOY

 

[Prafull]

Good work Twave. All 3 of your answers are right.
Here we go again.

4th question:

793 $ is divided into 3 parts as such that their amount after 2,3, and 4 years may be equal, the rate of simple interest being 5%. find ratio between these parts.