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?
Advertisements
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)`
Find the excluded values, of the following expression
`(x^2 + 6x + 8)/(x^2 + x - 2)`
Simplify `(4x^2y)/(2z^2) xx (6xz^3)/(20y^4)`
Simplify `(5"t"^3)/(4"t" - 8) xx (6"t" - 12)/(10"t")`
If A = `(2x + 1)/(2x - 1)`, B = `(2x - 1)/(2x + 1)` find `1/("A" - "B") - (2"B")/("A"^2 - "B"^2)`
Solve `1/3` (x + y – 5) = y – z = 2x – 11 = 9 – (x + 2z)
One hundred and fifty students are admitted to a school. They are distributed over three sections A, B and C. If 6 students are shifted from section A to section C, the sections will have equal number of students. If 4 times of students of section C exceeds the number of students of section A by the number of students in section B, find the number of students in the three sections
In a three-digit number, when the tens and the hundreds digit are interchanged the new number is 54 more than three times the original number. If 198 is added to the number, the digits are reversed. The tens digit exceeds the hundreds digit by twice as that of the tens digit exceeds the unit digit. Find the original number
At t minutes past 2 pm, the time needed to 3 pm is 3 minutes less than `("t"^2)/4`. Find t.
The number of seats in a row is equal to the total number of rows in a hall. The total number of seats in the hall will increase by 375 if the number of rows is doubled and the number of seats in each row is reduced by 5. Find the number of rows in the hall at the beginning.
