Q3.

If \(9^{x} - 9^{x-1} = 72\), then the value of \(\frac{2x - 1}{2x + 3}\) is:

Q4.

Two trains, X and Y, are running on parallel tracks. Train X is 200 m long and travels at 72 km/hr. Train Y is 300 m long. If the trains are traveling in opposite directions, they pass each other completely in 15 seconds. If the trains were traveling in the same direction, how long would it take for the faster train to overtake the slower one?

Q5.

A shopkeeper offers the following schemes on toys of the same marked price. 

(A) Successive discounts of 44% and 12% on any number of toys bought. 

(B) Successive discounts of 18%, 43% and 23% on any number of toys bought.

 (C) 8% discount on the first 4 toys and 38% discount on each toy thereon. 

(D) On buying ten items, the customer is billed for only seven items. 

A customer wants to buy 10 toys. Which of the above schemes is the least beneficial to her?