会的进递等式0.79x0.46+7.9x0.24+11.4x0.07969316.931/69.31（3.4x4.8x9.5）/（1.9x1.7x2.4）1990x198.9-1989x198.8要巧算的~·

Question

会的进 递等式
0.79x0.46+7.9x0.24+11.4x0.079
69316.931/69.31
（3.4x4.8x9.5）/（1.9x1.7x2.4）
1990x198.9-1989x198.8
要巧算的~·

Answer 1

0.79x0.46+7.9x0.24+11.4x0.079
7.9x0.24+0.79x0.46+0.079x11.4
=0.079{(100x0.24)+(10x0.46)+(1x11.4)}
=0.079(24+4.6+11.4)
=0.079x40
=3.16
69316.931/69.31
=(69310+6.931)/69.31
=69310/69.31+6.931/69.31
=1000+0.1=1000.1
(3.4x4.8x9.5）/（1.9x1.7x2.4）
={2x1.7x2x2.4x5x1.9}/(1.9x1.7x2.4)
=2x2x5
=20
1990x198.9-1989x198.8
=1990x(198.8+0.1)-1989x198.8
=199+1990x198.8-1989x198.8
=199+198.8(1990-1989)
=199-198.8
=2