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The probability distribution of a discrete r.v.X is as follows.

x |
1 | 2 | 3 | 4 | 5 | 6 |

P(X = x) |
k | 2k | 3k | 4k | 5k | 6k |

Complete the following activity.

**Solution:** Since `sum"p"_"i"` = 1

P(X ≤ 4) = `square + square + square + square = square`

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#### Solution

Since `sum"p"_"i"` = 1

k + 2k + 3k + 5k + 6k = 1

∴ 21k = 1

∴ k = `1/21`

P(X ≤ 4) = P(X = 1) + P(X = 2) + P(X = 3) + P(X = 4)

= k + 2k + 3k + 4k

= **`1/21 + 2/21 + 3/21 + 4/21`**

= **`10/21`**

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