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Single digit numbers are from 1 to 9 so in that total digits used = 9. From 10 to 99.there are 90 numbers of 2 digits , so here digit used = 90 x 2 = 180 From 100 to 250 = 3 x151 = 453 (as all are of 3 digit number). So number of digits required to first 250 natural number = 9 + 180 + 453 = 642
A takes 3 hours more while swimming upstream than downstream. His speed in still water is 12 km/hr. The speed of stream is 4 km/hr. What is the distance?
If the sum of upstream and downstream speed is 48 km/hr and the speed of the current is 4 km/hr. Then find time taken to cover 84 km in downward?
A boat can cover 140 km in downstream in 14 hours and 96 km in upstream in 12 hours. Find the distance travelled by the boat in still water in 5 hours.
A boat goes 52 km in upstream in 4 hours and takes 3 hours to complete a distance of 15 km in downstream. Find the speed of boat in still water.