Question
A boat takes 8 hours to travel 42 km upstream and 81 km
downstream combined. In another instance, it covers 48 km upstream and 54 km downstream in 7 hours. Determine the time the boat would need to travel 90 km in still water.Solution
Let the upstream and downstream speeds of the boat are x km/h and y km/h. So according to question: 42/x + 81/y = 8 And, 48/x + 54/y = 7 Let 1/x = a and 1/y = b So 42a + 81b = 8 ………. (i) And 48a + 54b = 7 …….. (ii) Solving (i) and (ii) we get a = 1/12 and b = 1/18 So x = 12 and y = 18 So the upstream and downstream speeds of the boat are 12 km/h and 18 km/h respectively. So the speed of the boat in still water = (12 + 18)/2 = 15 km/h So the time taken by the boat to cover 90 km in still water = 90/15 = 6 hoursÂ
In calcareous soil, effervescence is visible when treated with diluted 0.1 N HCl due to release of which of the following?
Which of the following property of soil is not influenced by tillage operations?
Local control is not applied for the design:
Tillers cut near base at 45° angle and developing buds or ripening grains chewed are the damaging symptoms of _____
The disc plough is designed to work in all types of soil for functions such as soil breaking, soil raising, soil turning and soil mixing. Tilt angle of ...
In a vector having two or more target sites in a non essential portion of DNA for the cloning is known as ___
Which of the following is not correct about zero tillage? Â
Conversion of rotary motion into mechanical power to move the vehicle wheels is done by
How is thermal efficiency different in diesel and petrol engines?
Fruit and shoot borer is an important pest of;
Relevant for Exams:
