Question 10:

Suppose there are 10 students in your class. You want to select three out of them. How many samples are possible?


Population = 10

No. of possible samples are 30 (=10 × 3)

This answer is wrong... please corelate your answers

total number of students 10
3 has to be selected out of 10.
we can select any combination of 3 students out of 10.
formula for combination is
Crn=n ιn-r ι*r ι, where n ι=n*n-1*n-2*n-3*......
n is the total number of observations and r is the number of observations which is to be selected.
here, n = 10
        r = 3
C310= 10 ι 10-3 ι*3 ι=10*9*8*7ι7ι*3 ι=10*9*83*2*1=120 ways

  • 8

if you have learnt Combinations you'll understand this:out of 10 students 3 are to be taken out. it can be done in 10C3 ways:( i hope u know factorial)10!/10-3!*3!=10!/7!*3! =10*9*8/3*2*1 ..............[7... gets cancelled]since 3 will cancel 9 and 2 will cancel 10, it will be equal to5*3*8=120therefore students can be chosen in 120 ways

  • 4
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