Question

小红和小明分别读两本页数相同的书,小红已读页数是小明未读页数的2/5,小明已读页数是小红未读页数的3/7.求小红未读与小

Answer 1

设,总页数为C,小红未读为A,则小红已读为C-A,

小明未读为B,则小明已读为C-B,

根据题意,C-A = (2/5)B C-B = (3/7)A

因为C相同,所以 (2/5)B+A = (3/7)A+B

A(1-3/7) = B(1-2/5)

A(4/7) = B(3/5)

A/B = (3/5)/(4/7) = 21/20

所以,小红未读与小明未读的页数比是21:20.