A can do a piece of work alone in 30 days. B is 25% less efficient than A, while C is $$33{1\over 3}$$ % more efficient than B. In how many days can A, B and C, working together, complete the work?

Directions: Find the wrong number in the following number series:

The ratio between Males who use their coupon in Pedicure to that of in Spa is 4: 5, while ratio between Females who use their coupon in Haircutting to that of in Spa is 6: 11. Find total number of people who use their coupons in Spa. 

Mahesh invests a sum of money which becomes Rs. 1344 in 3 years and Rs. 1536 in 7 years. How much had he invested?

The ratio of the number of boys and girls in the parade of students of a school is 9 : 7 respectively and the total number of students is 256. Find the number of girls?

The diameters of two cones are equal. If their slant heights are in the ratio 5: 2, then the ratio of curved surface areas of the cones is _________ .

If $$ {x+{1\over x}=7}$$ then $$ {x^{2}+{1\over {x^{2}}}=?}$$

The price of sugar is increased by 20%. As a result, a family has to decrease its consumption by 20%. The expenditure of the family on sugar is decreased by

What value will come in place of question mark (?) in the following questions?

(?)² + 1 = 212 + 172