51.

A can do a piece of work in 20 days and B in 15 days. With help of C, they finish the work in 5 days. C can alone do the work in

• 5 days

• 6 days

• 10 days

• 12 days

A spherical lead ball of radius 6 cm is melted and small lead balls of radius 3 mm are made. The total number of possible small lead balls is:

• 4250

• 4000

• 8005

• 8000

At what percentage above the cost price must an article be marked so as to gain 33% after allowing a customer a discount of 5%?

• 40%

• 45%

• 35%

• 47%

The four sides of a quadrilateral are in the  ratio of 2 : 3 : 4 : 5 and its perimeter is 280 m. The length of the longest side is:

• 100 m

• 150 m

• 175 m

• 180 m

Kamal has some apples. He sold 40% more than he ate. If he sold 70 apples, how many did he eat?

• 18

• 42

• 50

• 90

A train 100 m long is running at a speed of 120 km/hr. The time taken to pass a person standing near the lines is

• 1 sec

• 3 sec

• 5 sec

• 7 sec

If x² + 5x + 6 =  0,   then the value of  is:

If a + b = 5   and   a - b = 3, then the value of (a² + b²) is

• 17

• 18

• 19

• 20

A 8 cm long perpendicular is drawn from the centre of a circle to a 12cm long chord. The diameter of the circle is

• 10 cm

• 12 cm

• 16 cm

• 20 cm

The point equidistant from the sides of a triangle is called:

• Circumcenter

• Incentre

• Orthocentre

• Centroid