RRB Group D Probability

Count total balls = 5 + 3 + 2 = 10

Count favorable outcomes (red balls) = 5

Apply formula = 5/10 = 1/2 = 0.5 Answer: 1/2 or 50% Shortcut Trick #2 - Card Problems Quick Reference: Remember that a deck has 52 cards with 13 cards of each suit (hearts, diamonds, clubs, spades). Face cards are 12 in total (4 each of Jack, Queen, King)

Total possible outcomes when throwing two dice = 6 × 6 = 36

Find favorable outcomes for sum = 7 (1,6), (2,5), (3,4), (4,3), (5,2), (6,1) = 6 outcomes

Apply formula = 6/36 = 1/6 Answer: 1/6 Shortcut Trick #3 - Dice Sum Patterns: For two dice, sum of 7 has maximum probability (6/36), while sums of 2 and 12 have minimum probability (1/36 each). Common Mistake #1: Students often forget to consider all possible arrangements. For example, when drawing 2 balls from a bag, they count (Red, Blue) but forget (Blue, Red) as a separate case when order matters. Always check whether the problem requires considering order or not. Another frequent error is mixing up 'with replacement' and 'without replacement' scenarios. In 'with replacement', the total number of items remains the same for each draw. In 'without replacement', the total decreases after each draw, affecting subsequent probabilities.