次の値を計算せよ。
(1) 4P2 = ⋅4 3
=12
(2) 7P3 = ⋅ ⋅7 6 5
=210
(3) 5P4 = ⋅ ⋅ ⋅5 4 3 2
=120
(4) 5P5 = ⋅ ⋅ ⋅ ⋅5 4 3 2 1
=120
(5) 8P1=8
(6) 10P3= ⋅ ⋅10 9 8
=720
(7) 12P2 =12 11⋅
=132
(8) 6P4 = ⋅ ⋅ ⋅6 5 4 3
=360
( 1)( 2) { ( 1)}
nPr =n n− n− n− −r です。
こういうものは,一般化するとわかりにくい印象を与えますね。
具体的な値で計算方法を納得しておきましょう。
37.nPr
(1) 12 (2) 210 (3) 120 (4) 120 (5) 8 (6) 720 (7) 132 (8) 360