Current location - Training Enrollment Network - Books and materials - The first volume of mathematics in primary school for three years: there are four books in the library, and Xiaoming wants to borrow two. How many different ways are there? How is it calculated?
The first volume of mathematics in primary school for three years: there are four books in the library, and Xiaoming wants to borrow two. How many different ways are there? How is it calculated?
Let four books be abcd,

abdominal muscle

alternating current

advertisement

B.C.

Bottom fuze (abbreviation of base detonating)

laser record

3+2+ 1=6.

A starts with ab, ac and ad.

Bc and bd with the beginning of B.

Cd no.1 middle school with the beginning of c.

3+2+ 1=6

This formula is used for this kind of problem.