Question

c) If the speed of an aeroplane is reduced by 40km/hr, it takes 1 hour 20 minutes
more to cover 1600 km. Find the speed of the aeroplane.

Answer 1

Answer:

The speed of the aeroplane is 400km/hr

Step-by-step explanation:

Please Mark me as brain list!!

Answer 2

Answer:

hey here is your answer in above pics

pls mark it as brainliest

Step-by-step explanation:

$so \: let \: the \: original \: speed \: of \: aeroplane \: be \: x \: km \div hr$

$so \: we \: know \: that \\ speed = distance \div time \\ ie \: time = distance \div speed$

$so \: total \: distance \: covered = 1600 \: km \\ so \: \: original \: time \: taken \: by \: aeroplane \: ie \: t1 = 1600 \div x \: hours \\ \\ when \: the \: speed \: is \: reduced \: by \: 40 \: km \div hr \\ time \: taken \: ie \: t2 = 1600 \div x - 40 \: hr$

$so \: here \: \\ we \: know \: that \: 1 \: hour = 60 \: mins \\ thus \: 1 \: min = 1 \div 60 \: th \: hour \\ similarly \: 1 \: hour + 20 \: mins = 60 \: mins + 20 \: mins = 80 \: mins \: \\ so \: 80 \: mins = 80 \div 60 \: th \: hour$

$here \: t2 > t1 \\ according \: to \: given \: condition \\ (1600 \div x - 40) - (1600 \div x) = 80 \div 60 \\ ie \: 1600 \times (1 \div (x - 40) - 1 \div x) = 4 \div 3$

$so \: 1600(x - (x - 40) \div x(x - 4) = 4 \div 3 \\ 1600(x - x + 4 )\div x.square - 40x = \div 3 \\ so \: 1600 \times 40 \div x.squre - 40x = 4 \div 3 \\ \\ ie \: 1600 \times 10 \div x.square - 40x = 1 \div 3 \\ x.square - 40x = 16000 \times 3$

$ie \: x.square - 40x = 48000 \\ so \: x.square - 40x - 48000 = 0$

$to \: solve \: this \: so \: formed \: quadratic \: equation \: use \: formula \: method \: rather \: than \: completing \: square \: or \: factorisation \: method \\ \\ this \: step \: (calculation \: part) \: is \: in \: pic \: uploaded \: above$

$thus \: the \: original \: speed \: of \: aeroplane \: was \: 240 \: km \div hr$