By selling mangoes at the rate of 64 for Rs. 2,000, the vendor loses 40%. How many should he sell for Rs. 1000 so as to gain 20%?

The average age of three men is 50 years and their ages are in the proportion 3:5:7. The age of the youngest man is:

The area of a triangular metal plate with base 88 cm and altitude 64 cm is to be reduced to one-fourth of its original area by making a hole of circular shape at the center. The radius of this hole will be:

If a and b are positive real numbers and a ∗ b denotes √(a × b), what is the value of 8 ∗ (4 ∗ 16)?

Find the value of √[(2 + √3)/(2 − √3)], correct to three places of decimal.

If x = ⁶√5 (sixth root of 5) and y = ⁵√4 (fifth root of 4), which of the following is true?

A mixture of petrol and kerosene weighing 5 kg contains 5% kerosene. How much more kerosene (approx.) must be added into it to make it 10%?

In the figure, PQ is a diameter of the circle. Angle PQS = 35°. Find angle QRS. (R and S are points on the circle on opposite sides of PQ; chords RQ, RS and SQ are drawn.) [Figure: see page 6 of source PDF]

A student who gets 20% marks fails by 20 marks, but another student who gets 36% marks gets 44 marks more than minimum passing marks. Find the maximum number of marks and percentage necessary for passing.