Question

简便计算 一定要有过程。08

1/4 ＋ 1/28 ＋ 1/70 ＋ 1/130 ＋ 1/208

Answer 1

1/4X7=28 1/4+1/28=2/7
.... 2/7+1/70=3/10
.... 3/10+1/130=4/13
.... 4/13+1/208=5/16

Answer 2

=7/28 + 1/28 ＋ 1/70 ＋ 1/130 ＋ 1/208
=8/28 + 1/70 ＋ 1/130 ＋ 1/208
=2/7 + 1/70 + 1/130 + 1/208
=21/70 + 1/130 + 1/208
=3/10 + 1/130 + 1/208
=40/130+1/208
=4/13+1/208
=65/208
=5/16

Answer 3

1/4 ＋ 1/28 ＋ 1/70 ＋ 1/130 ＋ 1/208
=1/(1*4)+1/(4*7)+1/(7*10)+1/(10*13)+1/(13*16)
=(1/3)[1-1/4+1/4-1/7+…………+1/13-1/16]
=(1/3)(1-1/16)
=5/16

Answer 4

1/4 ＋ 1/28 ＋ 1/70 ＋ 1/130 ＋ 1/208
=[(1-1/4)+(1/4-1/7) +(1/7-1/10)+(1/10-1/13)+(1/13-1/16)]/3
=(1-1/16)/3
=(15/16)/3
=5/16

Answer 5

=1/3(1-1/4)+1/3(1/4-1/7)+1/3(1/7-1/10)+1/3(1/10-1/13)+1/3(1/13-1/16)
=1/3(1-1/16)
=5/16