Percenatge Problem

[Karthik12]

1. 50 kg alloy has 60% leadand the balance Tin. How much lead is to be added to make it 75% of the alloy?
a. 80kg
b. 50kg
c. 30Kg
d. 20kg


2. In examination of 7 subjects with maximum 100 marks in each, I scored 40% in all. Average marks in 3 subjects were 48 while the highest marks scored among these three subjects were 64. If passing marks in any subject were 35, then what was the minimum number ofsubjects in which I failed?
a. 1
b. 2
c. 0
d. none of these

[sudhir3127]

IMO 30 kgs of alloy must be added.

[Karthik12]

Hai Sudhir.....I want explained answers of the above questions.....I dont know how to proceed the above problems.......can u help me?

[sudhir3127]

assumme that total after increased lead will be 50+X

Tin would remain the same.

lead would be 30+x ( 60% 0f 50)

equation 50+x = 20+ (50+x)*75%

solve this to get X = 30.

[raunekk]

is the 2nd question correct...???

[sudhir3127]

Answer is 1 for 2nd question..

average of 3 students us 48 = 144 . one subject he scored 64 hence two subjects he scored 144-64 =80 ( minimum is 35 hence he wud have cleared those 2 subjects)

total he scored 40% which is 7*100*40% = 280

hence the average of 4 subjects = 280- 144 ( avg of 3 subjects)
= 136
minimum he shud get 35 in each subject to pass.. hence 35*4 = 140

therefore the minimum no the subjects he would have failed is 1 .

let us know the OA.

[Karthik12]

ya.....2nd question is right...

[Karthik12]

Thanks Sudhir...