the number of n digit number which consist of the digit 1 and2 only if each digit is to be used atleast once is equal to 510 then n equal to

a]7

b)8

c)9

d)10

Given that (1+5x)⁴ = 1 + Px + Qx² + Rx³ +..... Find the values of P - 2Q + 3R

9 men and 15 boys working 10 hours a day can make 12 pillars in 42 days, in how many days will 12 men and 22 boys working 8 hours a day can make pillars 4 times the previous number?

In the given figure, PQ is a tangent at a point C to a circle with centre O. If AB is a diameter, find angle PCA + angle BCQ? 

for any two sets A and B (A-B)U(B-A)U (A intersection B)

If someone has got 150 out of 200 marks in term 1 exam and 160 out of 200 marks in term 2 exam then what is the percentage in  30:70