Chat with tutor

Ask Questions, Get Answers


How many 7 digit numbers are there using the digits,1,2,3 and '2' should occur 2 times in each of the number?

1 Answer

Since 2 occur twice, to fix 2 $2^s$, we have to choose
any two places out of 7 (7digit numbers)
This can be done in $^7C_2$ ways.
Remaining 5 places can be fixed by any of the two numbers, 1or 2
This can be done in $2^5$ ways.
$\therefore$ The required number of 7 digit numbers = $2^5.^7C_2$
Help Clay6 to be free
Clay6 needs your help to survive. We have roughly 7 lakh students visiting us monthly. We want to keep our services free and improve with prompt help and advanced solutions by adding more teachers and infrastructure.

A small donation from you will help us reach that goal faster. Talk to your parents, teachers and school and spread the word about clay6. You can pay online or send a cheque.

Thanks for your support.
Please choose your payment mode to continue
Home Ask Homework Questions
Your payment for is successful.
Clay6 tutors use Telegram* chat app to help students with their questions and doubts.
Do you have the Telegram chat app installed?
Already installed Install now
*Telegram is a chat app like WhatsApp / Facebook Messenger / Skype.