Question: In January, the value of a stock increased by 50%; and in February, it decreased by 20%. In March, it increased by 25%; and in April, it decreased by 10%. If a person invested Tk. 200 in the stock on January 1 and sold it at the end of April, what was the percentage change in the price of the stock?

Solution:
At the end of January,
The value of the stock is = Tk. 200 + 50% of (Tk. 200)
= Tk. 200 + Tk. 100 = Tk. 300.

At the end of February,
The value of the stock is = Tk. 300 - 20% of (Tk. 300)
= Tk. 300 - Tk. 60 = Tk. 240.

At the end of March,
The value of the stock is = Tk. 240 + 25% of (Tk. 240)
= Tk. 240 + Tk. 60 = Tk. 300.

At the end of April,
The value of the stock is = Tk. 300 - 10% of (Tk. 300)
= Tk. 300 - Tk. 30 = Tk. 270.

Now, the percentage change in price is,
= (Change in price/Original price) × 100%
= (270 - 200)/200 × 100%
= (70/200) × 100%
= 35%

Question: A, B and C invested in a business. The ratio of A's investment to B's is 4 : 5 and B's to C's is 5 : 6. If the total profit is Tk. 75000, how much profit did B get?

সমাধান:
প্রদত্ত অনুপাতে,
A : B = 4 : 5
B : C = 5 : 6

⇒ A : B : C = 4 : 5 : 6

মোট অনুপাত = 4 + 5 + 6 = 15

সুতরাং, B এর লাভ = (5/15) × 75000
= 25000 Tk.