Class 10 Important Math Question

1.  Which term of the A.P. 3, 15, 27, 39, …… will be 120 more than its 21st term?

2. Find c if the system of equations cx + 3y + (3 – c) = 0, 12x + cy – c = 0 has infinitely many solutions?

3. A father’s age is three times the sum of the ages of his two children. After 5 years his age will be two times the sum of their ages. Find the present age of the father. 

4. Prove that (sin θ + cosec θ )² + (cos θ + sec θ)² = 7 + tan² θ + cot² θ.