Quantitative Aptitude - Arithmetic Ability Questions

In figure, DE || BC. If DE = 3 cm, BC = 6 cm and area of ΔADE = 15 sq cm, then the area of ΔABC is

If  x=2+32-3, then what is the value of x+1/x ?

If cos(A-B) - cos(A+B) = x, then the value of x is

If the side AB of an equilateral triangle ABC is equal to 12 cm. Calculate the length( in cm) of the AO, if O is the centroid of the triangle.

The difference between the ages of mother and son was 21 when mother's age was 43. If father is elder by 3 years to mother, what will be the difference between the ages of son and father when father attains 50 years?

A shop keeper purchased 10 kg of rice and 20 kg of sugar at Rs. 75 and Rs. 85 per kg respectively. On selling, he gained 20% on rice and 10% on sugar. What was the total sale price?

How much is the maximum % discount that sheela can offer to her customer on her Marked Price so that she sells her product at no profit or loss, if she had already marked her product by 25% more than the cost price?

If X and Y are the two digits of the number 347XY such that the number is completely divisible by 80, then what is the value of X + Y?