Advertisements
Advertisements
प्रश्न
A boat takes 1.6 hours longer to go 36 kms up a river than down the river. If the speed of the water current is 4 km per hr, what is the speed of the boat in still water?
उत्तर
Let the speed of the boat in still water be “x”
Time taken to go for up of a river = `36/(x + 4)`
By the given condition
`36/(x - 4) - 36/(x + 4)` = 1.6
`(36(x + 4) - 36(x - 4))/((x + 4)(x - 4)) = 16/10`
`(36[x + 4 - (x - 4)])/(x^2 - 16) = 16/10`
`(36 xx 8)/(x^2 - 16) = 16/10`
16(x2 – 16) = 36 × 8 × 10
x2 – 16 = `(36 xx 8 xx 10)/16`
x2 – 16 = 180
x2 = 180 + 16
x2 = 196
x2 = `sqrt(196)`
= ± 14
The speed of the boat in still water = `(14"km")/"hr"`
APPEARS IN
संबंधित प्रश्न
Reduce the following rational expression to its lowest form
`(x^2 - 11x + 18)/(x^2 - 4x + 4)`
Reduce the following rational expression to its lowest form
`(9x^2 + 81x)/(x^3 + 8x^2 - 9x)`
Reduce the following rational expression to its lowest form
`("p"^2 - 3"p" - 40)/(2"p"^3 - 24"p"^2 + 64"p")`
Simplify `(5"t"^3)/(4"t" - 8) xx (6"t" - 12)/(10"t")`
Simplify `(x^3 - y^3)/(3x^2 + 9xy + 6y^2) xx (x^2 + 2xy + y^2)/(x^2 - y^2)`
Simplify `(x + 2)/(x + 3) + (x - 1)/(x - 2)`
If A = `x/(x + 1)` B = `1/(x + 1)` prove that `(("A" + "B")^2 + ("A" - "B")^2)/("A" + "B") = (2(x^2 + 1))/(x(x + 1)^2`
Simplify `(1/("p") + 1/("q" + "r"))/(1/"p" - 1/("q" + "r")) xx [1 + ("q"^2 + "r"^2 - "p"^2)/(2"qr")]`
Is it possible to design a rectangular park of perimeter 320 m and area 4800 m2? If so find its length and breadth.
Two farmers Thilagan and Kausigan cultivates three varieties of grains namely rice, wheat and ragi. If the sale (in ₹) of three varieties of grains by both the farmers in the month of April is given by the matrix.
`{:("April sale in" ₹)/("rice" "wheat" "ragi"):}`
A = `[(500, 1000, 1500),(2500, 1500, 500)]"Thilagan"/"Kausigan"`
and the May month sale (in ₹) is exactly twice as that of the April month sale for each variety.
What is the average sales for the months of April and May
