SOLUTION: An electronics store receives a shipment of 30 graphing calculators, including 7 that are defective. 4 of the calculators are selected to be sent to a local high school. How many s

Question 868419: An electronics store receives a shipment of 30 graphing calculators, including 7 that are defective. 4 of the calculators are selected to be sent to a local high school. How many selections can be made using the original shipment?
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
Anuj alone does the job in 20 days.
every third day he takes help
so he takes help on 6 days
anuj does 1/20 of job in 1 day
and on 6 days they do 1/20+1/30+1/60 of the job = 1/10 of the job
On 6 days they do 6/10 of the job
and on 14 days 14/20 of the job is done
in 20 days they can do 6/10 + 14/20 of the job
=26/20 of the job in 20 days
so 26/20 of the job 20 days
1 job = 400/26= 15.38 days
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