Question

a shopkeeper sells 3 packet of chips for rs. 42 . Rohan buys 5 such packets. how much money did he spent

options-
a. 60
b. 65
c. 75
d. 90​

Answer 1

let the no of packets be x  

let the cost of each packet be y

so xy = 80 ⇒ y = 80/x

so if he would have bought 4 more packets for the same amount, each packet would have cost rupees 1 less  (x+4)(y-1)=80

⇒ (x+4)(80/x-1)=80

⇒ x² + 4x - 320 = 0

⇒ x² + 20x - 16x - 320 = 0

⇒ (x - 16)(x + 20) = 0

so x = 16 or - 20  

so number of packets can't be negative

so 16 packets he bought ANSWER

this is just a similar question u can apply it to your answer