vso 寫道:
Let X = time required for peeling 52 pineapples
In X minutes,
Worker A is able to peel X/2 pineapples
Worker B is able to peel X/3 pineapples
Worker C is able to peel X/4 pineapples
X/2 + X/3 + X/4 = 52
(6X + 4X + 3X) / 12 = 52
(6 + 4 + 3)X / 12 = 52
13X / 12 = 52
13X = 52 * 12
X = 52 * 12 / 13
X = 48
Time required for peeling 52 pineapples is 48 minutes

jean_ko 寫道:
可以試下這樣諗:
A&B&C 的 LCM (由 2&3&4 分鐘計出來的) 是 12 分鐘.
即是 12分鐘後 他們完成削菠蘿的數目會是整數,
A after 12 min 6 pcs
B after 12 min 4 pcs
C after 12 min 3 pcs
12分鐘 (當是 1 part 時間) 後 , 三個人會削完 ( 6 + 4 + 3 = 13 ) 13 個菠蘿.
所以, 削完菠蘿52個是要用 (52除 13 ) 即是4 part 時間;
總共是用了 (12 x 4 ) 48 分鐘.