At a construction site, 200 workers were working on a building which is scheduled to end within 250 days. After 30 days, 20 workers leave the job. How many more days will it take to complete the work? 

If $$ {x^{4}+x^{2}y^{2}+y^{4}={21\over256}}$$ and $$ {x^{2}+xy+y^{2}={3\over16}}$$ then $$ {2(x^{2}+y^{2})}=?$$

The LCM of two numbers is 864 and their HCF is 144. If one of the numbers is 288, the other number is:

A, B and C did certain investments and the ratio of their time periods is 3 : 2 : 7respectively. Ratio of  the profits of A, B and C is 4 : 3 : 14 respectively. What is the ratio of the investments of A, B and C?

$$ {I.2x^{2}-{9x}+10=0}$$
$$ {II.2y^{2}-13y+20=0}$$

If the area of a circle is 9π sq.cm then it circumference is

Two men are standing on opposite ends of a bridge 1200 meters long. If they walk towards each other at the rate of 5m/minutes respectively, in how much time will they meet each other?

Find the standard deviation of the following data (rounded off to two decimal places). 5, 3, 4, 7