جيڪڏهن توهان هاڻ خريد ڪيو ٿا ، 30 سيڪڙو رعايت حاصل ڪريو
Solution Calculating the expectation. Let time T be the number of draws needed to collect all n coupons, and let t i be the time to collect the i-th coupon after i − 1 coupons have been collected. Then = + +.Think of T and t i as random variables.Observe that the probability of collecting a new coupon is = = +.Therefore, has geometric distribution with expectation = +.
ڪوپن ڪوڊ ڏيکاريو