There are three white and five black balls in a bag. In how many ways four balls should be selected such that there is at least one ball of each color?

Explanation

CASE I: Selection of 1 White and 3 black balls Req number of ways = 3C1 × 5C3 = 30 CASE II: Selection of 3 White and 1 black balls Req number of ways = 3C3 × 5C1 = 5 CASE III: Selection of 2 White and 2 black balls Req number of ways = 3C2 × 5C2 = 30 Therefore, req num of ways = 30+5+30 = 65. Sol (61-65) For company A Total cost price of masks = 20 × 100 = 𝑅𝑠. 2000 Total selling price of masks = 120 × 20 × 40 + × 20 × 60 = 960 + 1320 = 𝑅𝑠. 2280 For company B Total cost price of masks= 150 × 40 = 𝑅𝑠. 6000 Total marked price of the mask = 150 × 40 × 150 = 𝑅𝑠. 9000 Total selling price of masks = 9000 × 90 = 𝑅𝑠. 8100 For company C Let total masks be x units Selling price = 100 × 𝑥= 10800 𝑥= 108 Total cost price of masks = 10800×100 = 𝑅𝑠. 80 125×108 6 www.bankersadda.com | www.ssca S61. Ans. (d) Sol. Required percentage = 100+108 × 100 = 138 % S62. Ans. (d) Sol. Required difference = 20 − 9000−8100 = 20 − 6 = 14 S63. Ans. (c) Sol. Total cost price = 2000 + 6000 + 8640 = 𝑅𝑠. 16640 S64. Ans.(e) Sol. Total selling price = 2280+8100+10800= Rs.21180 S65. Ans. (e) Sol. Required difference = 70 × 150 − 60 × 100 = 100 100 105 −60 = 45 𝑚𝑎𝑠𝑘𝑠 S66. Ans.(d) Sol. I. (2x – 7)² = 25 ⇒ 2x – 7 =± 5 ⇒ x = 1, 6 II. (4𝑦−1)2 = 9 ⇒4𝑦−1 = ±3 𝑦= 1, −1 𝑥≥𝑦 adda.com | www.careerpower.in | Adda247 App