Question

the cost of banana is increased by 1 rupee per dozen ,one can get 2 dozen less for 840 rupee .find the original cost of one dozen of banana please solve this quadratic equation carefully ​

Answer 1

hey mate!!!

solution:

let the original price be x rupees.

no. of bananas= 840/x

now,.

after increased price,

no. of bananas= 840/x+1

therefore,

840/x-840/x+1=2

840(x+1)-840x/x^2+x=2

840/x^2+x=2

840=2x^2+2x

2x^2+2x-840=0.

therefore,

required quadratic equation:

x^2+x-420=0......(dividing by 2)

now,

by Factorization method,

x^2+21x-20x-420=0

x(x+21)-20(x+21)=0

therefore

(x+21)(x-20)=0

x=-21 or x= 20

we know,

cost of bananas cannot be negative,

so x=-21 is discarded.

therefore,

original cost of bananas= ₹20

hope this helps!!☺✌❤