問50
頻出度★★★
プロジェクトチームのメンバがそれぞれ1対1で情報の伝達を行う必要がある。メンバが10人から15人に増えた場合に，情報の伝達を行うために必要な経路は幾つ増加するか。
平成29年度 春期 ITパスポート試験 問50
マネジメント系プロジェクトマネジメント › プロジェクトマネジメント
This question's explanation and your answers so far.
解説
問 50
Incorrectア
5 is merely the increase in the number of people (15−10). The question asks for the increase in the number of paths, not the increase in the number of people, so it is wrong.
Incorrectイ
10 is the original number of people before the increase, and has nothing to do with the number of paths. The increase in paths is the difference from 45 paths to 105 paths, which is 60, not 10, so it is wrong.
- ウ
正解 The number of paths for all members to communicate with each other one-to-one can be found with the combination of choosing 2 people out of n, C(n,2)=n(n-1)÷2. With 10 people it is 10×9÷2=45 paths, and with 15 people it is 15×14÷2=105 paths. The question asks for the increase in the number of paths, so 105−45=60. Therefore the correct answer is ウ, namely 60.
Incorrectエ
105 is the total number of paths when there are 15 people. Because it does not subtract the 45 paths that already exist with 10 people, it is too large to be the increase in the number of paths, so it is wrong.
ここがポイント
- The number of paths for all n people to communicate one-to-one with each other is found with the combination C(n,2)=n(n-1)÷2 (the number of communication paths in Project Communications Management).
- When asked for the increase, subtract the before-value from the after-value (105−45=60). Do not confuse it with the total (エ) or the difference in the number of people (ア).
用語