(1)工程队修一条水渠,第一天修了全长的1/4,第二天修了全长的30%,还剩下900千米没修.这条水渠全长多少米?
2个回答

(1)

900 / (1-1/4-3/10)

=900 / (1- 5/20 -6/20)

=900 / (9/20)

=2000 千米

(2)

25-25×99%

=25 ×(1-0.99)

=25 × 0.01

=0.25

(3)

3-3/8÷(7/16)-1/7

=3-6/7-1/7

=2