প্রশ্ন: আয়না থেকে 5 ফুট দূরত্বে দাঁড়িয়ে, আয়না থেকে আপনার প্রতিবিম্ব কতদূরে দেখা যাবে? 

সমাধান: 
আমরা জানি, 
আয়না থেকে লক্ষ্যবস্তুর দূরত্ব ও প্রতিবিম্বের দূরত্ব সমান। 
অতএব, প্রতিবিম্ব 5 ফুট দূরে দেখা যাবে।

Question: Working 5 hours a day, A can complete a work in 9 days and working 9 hours a day, B can complete the same work in 10 days. Working 6 hours a day, they can jointly complete the work in - 

Solution: 
Working 5 hours a day, for 9 days, A can finish the work in = (5 × 9) = 45 hours
Working 9 hours a day, for 10 days, B can finish the work in = (9 × 10) = 90 hours

both together can do in one hour = 1/45 + 1/90
= (2 + 1)/90
= 3/90
= 1/30

so, it will take them 30 hours to do the work.

hence, working 6 hours a day, they need = 30/6 = 5 days

So they will complete the work in 5 days working 6 hours each day.

Question: A man rows downstream at 32 km/h and rows upstream at 22 km/h. At what speed can he row in still water?

Solution:
Given,
Man rows downstream = 32 km/h
Man rows upstream = 22 km/h
We know that,
Speed in still water = (Downstream speed + Upstream speed​) ÷ 2
= (32 + 22) ÷ 2
= 54 ÷ 2
= 27 km/h