Box I contain three cards bearing numbers 1,2,3; box II contains five cards bearing numbers 1,2,3,4,5; and box III contains seven cards bearing numbers 1,2,3,4,5,6,7. A card is drawn from each of the boxes. Let xi be the number on the card drawn from the ith box i=1,2,3.The probability that x1,x2 and x3 are in arithmetic progression, is ?

Box I contain three cards bearing numbers 1,2,3; box II contains five

1.	Box I contain three cards bearing numbers 1,2,3; box II contains five cards bearing numbers 1,2,3,4,5; and box III contains seven cards bearing numbers 1,2,3,4,5,6,7. A card is drawn from each of the boxes. Let xi be the number on the card drawn from the ith box i=1,2,3.The probability that x1,x2 and x3 are in arithmetic progression, is ?
Answer» Box I contain three cards bearing numbers 1,2,3; box II contains five cards bearing numbers 1,2,3,4,5; and box III contains seven cards bearing numbers 1,2,3,4,5,6,7. A card is drawn from each of the boxes. Let $x_{i}$ be the number on the card drawn from the $i^{t h}$ box $i = 1, 2, 3.$ The probability that $x_{1}, x_{2}$ and $x_{3}$ are in arithmetic progression, is ?