Periyar University 2008 B.E Electronics

51) The total expense of a boarding house is partly fixed and partly variable with the number of boarders. The charge is Rs.70 per head when there are 25 boarders and Rs.60 when there are 50 boarders. obtain the charge per head when there are 100 boarders.

a) 65

b) 55

c) 50

d) 45

Sol: let a = fixed cost and

k = variable cost and n = number of boarders

Total cost when 25 boarders c = 25*70 = 1750 i.e. 1750 = a + 25k

Total cost when 50 boarders c = 50*60 = 3000 i.e. 3000 = a + 50k

Solving above two eqns, 3000-1750 = 25k i.e. 1250 = 25k i.e. k = 50

Therefore, substituting this value of k in either of above two eqns we get

a = 500 (a = 3000-50*50 = 500 or a = 1750 - 25*50 = 500)

So total cost when 100 boarders = c = a + 100k = 500 + 100*50 = 5500

So cost per head = 5500/100 = 55





52) Amal bought five pens, seven pencils and four erasers. Rajan bought six pens, eight erasers and 14 pencils for an amount which was half more than what Amal had paid. What % of the total amount paid by Amal was paid for pens?

a) 37.5%

b) 62.5%

c) 50%

d) None of these

Sol: Let, five pens + seven pencils + four erasers = x rupees

So 10 pens + 14 pencils + eight erasers = 2*x rupees

Also mentioned, six pens + 14 pencils + eight erasers = 1.5*x rupees

So (10-6) = four pens = (2-1.5) x rupees

So four pens = 0.5x rupees => eight pens = x rupees

So five pens = 5x/8 rupees = 5/8 of total (note x rupees is total amt paid by

Amal) i.e. 5/8 = 500/8% = 62.5%


Ans: 62.5%





53) I lost Rs.68 in 2 races. My 2nd race loss is Rs.6 more than the 1st race. My friend lost Rs.4 more than me in the 2nd race. What is the amount lost by my friend in the 2nd race?

Sol: x + x+6 = rs 68

2x + six = 68

2x = 68-6

2x = 62

x=31

x is the amt lost in I race

x+ six = 31+6=37 is lost in 2nd race

Then my friend lost 37 + four = 41 Rs


Ans: 41 Rs





54) A face of the clock is divided into 3 parts. 1st part hours total is equal to the sum of the 2nd and 3rd part. What is the total of hours in the bigger part?

Sol: The clock normally has 12 hr

Earning:   Approval pending.