Mouth watering ice creams and mind watering problems-3

Sanjeet Raria owns a shop selling ice creams for pleasing you in the hot summer days. He has ice creams of 6 different flavors assuming each ice cream is of only one flavor. You go to his shop to fetch 4 ice creams, in how many ways can you get the ice creams if you want only 3 different flavors?


The answer is 60.

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3 solutions

We can choose 3 3 of the flavors in ( 6 3 ) = 20 \dbinom{6}{3} = 20 ways.

For each of these 20 20 combinations, since we must buy at least one of each of the 3 3 flavors, there are 3 3 choices for the remaining ice cream we intend to buy. This gives us a total of 20 × 3 = 60 20 \times 3 = \boxed{60} different ice cream combinations.

Nice and clear solution sir. ¨ \ddot \smile @Brian Charlesworth

Sandeep Bhardwaj - 5 years, 7 months ago
# Techintouch #
Mar 3, 2018

Select 3 ice creams from 6 in 6C3 ways and chose one in ice cream from selected ones in 3 ways,so total ways are =>6C3.3=20*3=60 Where "C" represents combinatorial.

Darshan Baid
Nov 4, 2015

Since only 1 ice cream can be of common flavor , it can be selected in ( 6 1 ) = 6 \dbinom{6}{1} = 6 ways . Not to select the remaining ice creams we can go for ( 5 1 ) × ( 4 1 ) = 20 \dbinom{5}{1} \times \dbinom{4}{1} = 20 . but here we did a blunder that if ice cream A is selected in first part and B in second then it can be that B is selected in first and A in second. So we have to divide it by 2. Our final answer becomes.

( 5 1 ) × ( 4 1 ) × ( 6 1 ) 2 = 60 \frac{ \dbinom{5}{1} \times \dbinom{4}{1} \times \dbinom{6}{1}}{2} = \boxed{60}

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