Engineering Maths - Percentage

1.  A and B enter into a partnership. A puts in the whole capital of  Rs.45000 on the condition that the profits will be equally divided after which B will pay A interest on half the capital at 10% p.a. and receive Rs.60 per month from A for carrying on the concern. What is the yearly profit, if B's income is half of A's income?

  • Option : B
  • Explanation :

    Interest on Rs.22500 = 0.1 x 22500 = 2250
    Charges for managing the concern = 60 x 12 = 720
    If yearly profit is x, then  B's share and A's share = (x/2)
    ∴(x/2)-2250 + 720
    = (1/2)((x/2) -720 + 2250)
    => x = Rs. 9180.

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3. The population of rats in a locality increases by 20% in one year.Observing this, the pest control committee decided to use a special kind of pesticide `xyz' which effectively kills 160 rats in 3 months. Just after 2 years, what is the net increase or decrease in the population of rats if, initially the population of rats is 3200 and pesticide is used effectively?

  • Option : C
  • Explanation :

    Growth rate of rat population in 3 months = 20 *(3/12) = 5%
    Increase in first 3 months = 3200 x 1.05 = 3360
    Also, net decrease in 3 months = 160
    Rat population = 3360 - 160 = 3200
    In the same way, after every 3 months, rat population remains the same
    Hence, even after 3 x 8 months i.e., 2 years, the population is maintained

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4. A man sells sugar to a tradesman at a profit of 20% but the tradesman becoming bankrupt pays only 80 paise in the rupee. How much percentage does the man gain or lose by his sale?

  • Option : C
  • Explanation :

    Let CP be Rs.x
    SP = 1.2 x But he gets only 1.2x * 0.8 = 0.96x
    Loss = 0.04x  
    Hence Loss % = 4.

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5. A camera costing 2550 is marked to be sold at a price, which gives a profit of 30%. What will be its selling price in a sale when 20% is taken off the marked price?

  • Option : B
  • Explanation :

    CP = Rs.550
    ∴ Marked price = 1.3x550 = Rs.715
    ∴ sales price = 0.8x715 = Rs.572.

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