Question
Ratio of number of boys to girls in a school is 3:5
respectively. Next year, 30 boys and 50 girls left the school and 90 boys and 110 girls joined the school. If ratio of number of boys to girls now becomes 4:6, then find the number of boys now.Solution
Let the initial number of boys and girls be '3n' and '5n' respectively. (3n - 30 + 90) :(5n - 50 + 110) = 4:6 Or, 6 X (3n + 60) = 4 X (5n + 60) Or, 18n + 360 = 20n + 240 Or, 2n = 120 Or, 'n' = 60 Required number of boys = 3 X 60 - 30 + 90 = 240
- A car was driven for 2.5 hours at a speed of 100 km/h and then for 1.5 hours at a speed of 80 km/h. Find the car's average speed for the total journey.
- A lion spots a deer 1.6 km ahead and starts chasing it. The lion runs at 20 m/s, and the deer runs at 12 m/s. How long will the lion take to catch the deer...
Anil travels a certain distance by car at a speed of 75 km/h and comes back to the starting point via same route by bike with speed of 45 km/h. Find the...
The aeroplane flies along a Square field @ 100, 200, 300 and 400 km/hours respectively. Then find the Average speed of the aeroplane during the whole jo...
A car travels from town P to town Q and back. The distance between P and Q is 240 km. On the onward journey (P to Q), the speed of the car is 20 km/h mo...
Train P starts from Lucknow to Dehradun at 11:55 am with an average speed of 27.5 m/s. Train Q starts from Dehradun to Lucknow at 1:35 pm with an averag...
- A taxi moving at a speed of 72 km/h covers a distance of 108 km. If the speed is increased by 50%, how much time (in minutes) will the taxi take to travel ...
A boy goes to school with a speed of 85 km/h and comes back with a speed of 40 km/h. find his average speed?
A train 'B' speeding with 100 kmph crosses another train C, running in the same direction, in 2 mins. If the length of the train B and C be 150m and 250...
On river, Q is the mid-point between two points P and R on the same bank of the river. A boat can go from P to Q and back in 12 hours and from P to R in...
Relevant for Exams:
