脱式计算.(能简算的要简算) ①1÷0.25+0.25÷1-2.5×0.1 ②1+2+3+4+5+6+5+4+3+2+1/6666662 ③2/2×4+2/4×6+2/6×8+2/8×10+2/10×12 ④1÷(1-0.99)-99÷(1
问题描述:
脱式计算.(能简算的要简算)
①1÷0.25+0.25÷1-2.5×0.1
②
1+2+3+4+5+6+5+4+3+2+1 6666662
③
+2 2×4
+2 4×6
+2 6×8
+2 8×10
2 10×12
④1÷(1-0.99)-99÷(1-0.999)
答
①1÷0.25+0.25÷1-2.5×0.1,
=4+0.25-0.25,
=4+(0.25-0.25),
=4+0,
=4;
②
,1+2+3+4+5+6+5+4+3+2+1 6666662
=
,36 6666662
=
,18×2 3333331×2
=
;18 3333331
③
+2 2×4
+2 4×6
+2 6×8
+2 8×10
,2 10×12
=
-1 2
+1 4
-1 4
+1 6
-1 6
+1 8
-1 8
+1 10
-1 10
,1 12
=
-1 2
,1 12
=
;5 12
④1÷(1-0.99)-99÷(1-0.999),
=1÷0.01-99÷0.001,
=100-99000,
=-98900.