The cost of 21 pencils and 9 clippers is Rs. 819. The cost price of 7 pencils and 3 clippers is = ?

3 pumps, working 8 hours a day, can empty a tank in 2 days. How many hours a day must 4 pumps work to empty the tank in 1 day?

A. 9

B. 10

C. 11

D. 12

If the cost of x metres of wire is d rupees, then what is the cost of y metres of wire at the same rate?

A. Rs. $$ {\frac{{{\text{xy}}}}{{\text{d}}}} $$

B. $${\text{Rs}}{\text{.}} {xd} $$

C. $${\text{Rs}}{\text{.}} {yd} $$

D. Rs. $$ {\frac{{{\text{yd}}}}{{\text{x}}}} $$

Running at the same constant rate, 6 identical machines can produce a total of 270 bottles per minute. At this rate, how many bottles could 10 such machines produce in 4 minutes?

A. 648

B. 1800

C. 2700

D. 10800

A fort had provision of food for 150 men for 45 days. After 10 days, 25 men left the fort. The number of days for which the remaining food will last, is:

A. $$29\frac{1}{5}$$

B. $$37\frac{1}{4}$$

C. 42

D. 54