Question
The speed of a boat in still water is 40% less than its
speed while moving downstream. If the boat takes 8 hours to travel 160 km upstream, how long will it take to cover a distance of 320 km downstream?Solution
ATQ, 
 
Let the downstream speed of the boat be ‘x’ km/h. 
 
So, the speed of the boat in still water = 0.60x km/h 
 
So, the speed of the stream = x – 0.60x = 0.40x km/h 
 
Upstream speed of the boat = 0.60x – 0.40x = 160/8 
 
0.20x = 20 km/h 
 
x = 100 km/h 
 
So, the time taken by the boat to cover 320 km downstream = 320/100 = 3.2 hours 
- What approximate value will come in place of the question mark (?) in the following question? (Note: You are not expected to calculate the exact value.) 
- 24.45% of 14.99% of 14999.78 + 159.80 = ?% of 1999.78 
- 15.78% of (287 + 302) + 12³ = ?% of 170 + 8 × 14 + 3² 
- ? = 65.78² ÷ (5.01⁵ + 7.02 × 33.33) + 33.33% of (290.88 × 23.09) 
- What approximate value will come in place of the question mark (?) in the following question? (Note: You are not expected to calculate the exact value.) 
- 1784.04 - 483.98 + 464.98 ÷ 15.06 = ?3 
- ? = 54.89 × 270.08 ÷ 135.17 + 464.35 ÷ 29.03 
- 233.98 + 73 × √35.95 - ? = 275.94 ÷ 3.99