Question
A boat covers 140 km downstream
and 80 km upstream in 4.5 hours. Additionally, it takes 5.25 hours to travel 224 km downstream and 50 km upstream. Calculate the distance the boat would travel in still water in 2.4 hours.Solution
Let the upstream and downstream speed of boat be 'U' km/h and 'D' km/h respectively. ATQ: (140/D) + (80/U) = 4.5 --------- (I) And, (224/D) + (50/U) = 5.25 -------- (II) On solving, 5 X equation (I) - 8 X equation (II) , we get, 5 X [(140/D) + (80/U) ] - 8 X [(224/D) + (50/U) ] = 5 X 4.5 - 8 X 5.25 Or, (700/D) + (400/U) - (1,792/D) - (400/U) = 22.5 - 42 Or, (1,092/D) = 19.5 Or, 'D' = (1,092/19.5) = 56 On putting value of 'D' in equation (I) , We get, (140/56) + (80/U) = 4.5 Or, 2.5 + (80/U) = 4.5 Or, (80/U) = 2 So, 'U' = 40 Speed of boat in still water = (1/2) X (downstream speed + upstream speed) = (1/2) x (56 + 40) = (96/2) = 48 km/h Therefore, required distance = 48 X 2.4 = 115.2 km
(500 × 6 ÷ 10) - (√256 + 8) = ?
22% of 400 + √ ? = 34% of 800 - 25% of 400
(2/5)(32% of 4500 – 440) = ? × 8
1550 ÷ 62 + 54.6 x 36 = (? x 10) + (28.5 x 40)
What will come in the place of question mark (?) in the given expression?
96 ÷ (9 - 6.6) + 17.5 X 6 = ? ÷ 8
13 X ? = 85 X 4 + √81 + 2
45% of 360 - 160 + ? = √324
((67)32 × (67)-18 / ? = (67)⁸
4567.89 - 567.89 - 678.89 = ?
82.3 × 644.7 × 723.4 × 815.85 = 72?
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