1 karansingh Asked: January 19, 20232023-01-19T00:36:17+05:30 2023-01-19T00:36:17+05:30In: CBSE Speed of a boat in still water is 15 km/h. It goes 30 km upstream and returns back at the same point in 4 hours 30 minutes. Find the speed of the stream. 1 important 5 mark board question cbseclass 10linear equations Share Facebook 1 Answer Voted Oldest Recent areeb123xyz 2023-01-20T10:50:10+05:30Added an answer on January 20, 2023 at 10:50 am Given: Speed of boat in still water = 15 km/hr. Let the speed of stream = x km/hr. Distance covered by boat in going upstream = Distance covered by boat in downstream = 30 km Speed of boat upstream = Speed of boat in still water – Speed of stream = (15 – x) km/hr. Speed of boat downstream = Speed of boat in still water + Speed of stream = (15 + x) km/hr. Since, Distance = Speed × Time ⇒ Time = Distance / Speed Time taken by boat upstream = Time taken by boat downstream Total time taken by the boat to go and come back to the same point = 4.5 hrs. ∴ Multiply and divide both sides by (15 – x)(15 + x): ⇒ 4.5 (225 – x^{2}) = 30(15 + x) + 30(15 – x) ⇒ 1012.5 – 4.5x^{2} = 450 + 30x + 450 – 30 x ⇒ 1012.5 – 4.5x^{2} = 900 ⇒ 4.5x^{2} = 112.5 ⇒ x^{2} = 25 ⇒ x = 5 But speed can’t be negative, ∴ Speed of the stream = 5 km/hr. 0 Reply Share Share Share on Facebook Share on Twitter Share on LinkedIn Share on WhatsApp Leave an answerLeave an answerCancel reply Featured image Select file Browse Add a Video to describe the problem better. Video type Youtube Vimeo Dailymotion Facebook Choose from here the video type. Video ID Put Video ID here: https://www.youtube.com/watch?v=sdUUx5FdySs Ex: "sdUUx5FdySs". Click on image to update the captcha. Save my name, email, and website in this browser for the next time I comment. Related Questions Find the values of k for which the pair of linear equations kx + 3y = k-2 and ... . Solve for x and y: 0.4x-1.5y = 6.5, 0.3x-0.2y=0.9. Solve graphically the system of linear equations 4x-5y +16=0 and 2x+y-6 = 0. Determine the vertices of the ... If the remainder on division of x3 + 2x2 + kx +3 by x – 3 is 21, ... Given that x – √5 is a factor of the polynomial x3 – 3√5x2 – 5x + 15√5, ...

Given: Speed of boat in still water = 15 km/hr.

Let the speed of stream = x km/hr.

Distance covered by boat in going upstream = Distance covered by boat in downstream = 30 km

Speed of boat upstream = Speed of boat in still water – Speed of stream = (15 – x) km/hr.

Speed of boat downstream = Speed of boat in still water + Speed of stream = (15 + x) km/hr.

Since, Distance = Speed × Time

⇒ Time = Distance / Speed

Time taken by boat upstream =

Time taken by boat downstream

Total time taken by the boat to go and come back to the same point = 4.5 hrs.

∴

Multiply and divide both sides by (15 – x)(15 + x):

⇒ 4.5 (225 – x

^{2}) = 30(15 + x) + 30(15 – x)⇒ 1012.5 – 4.5x

^{2}= 450 + 30x + 450 – 30 x⇒ 1012.5 – 4.5x

^{2}= 900⇒ 4.5x

^{2}= 112.5⇒ x

^{2}= 25⇒ x = 5

But speed can’t be negative, ∴ Speed of the stream = 5 km/hr.