题目内容
若将算式1994+
-1
+2
-3
+4
-5
+…+1992
-1993
的值化为小数,由小数点后第1个数字是( )
| 1 |
| 2 |
| 1 |
| 3 |
| 1 |
| 2 |
| 1 |
| 3 |
| 1 |
| 2 |
| 1 |
| 3 |
| 1 |
| 2 |
| 1 |
| 3 |
| A.4 | B.3 | C.2 | D.1 |
1994+
-1
+2
-3
+4
-…+1992
-1993
,
=2
-1
+4
-3
+…+1992
-1991
+1994
-1993
,
=(2-1)+(
-
)+(4-3)+(
-
)+…+(1992-1991)+(
-
)+(1994-1993)+(
-
),
=(1+
)×(1994÷2),
=
×997,
=
=1163
,
≈1163.167;
小数点后第1个数字是1.
故选:D.
| 1 |
| 2 |
| 1 |
| 3 |
| 1 |
| 2 |
| 1 |
| 3 |
| 1 |
| 2 |
| 1 |
| 2 |
| 1 |
| 3 |
=2
| 1 |
| 2 |
| 1 |
| 3 |
| 1 |
| 2 |
| 1 |
| 3 |
| 1 |
| 2 |
| 1 |
| 3 |
| 1 |
| 2 |
| 1 |
| 3 |
=(2-1)+(
| 1 |
| 2 |
| 1 |
| 3 |
| 1 |
| 2 |
| 1 |
| 3 |
| 1 |
| 2 |
| 1 |
| 3 |
| 1 |
| 2 |
| 1 |
| 3 |
=(1+
| 1 |
| 6 |
=
| 7 |
| 6 |
=
| 6979 |
| 6 |
=1163
| 1 |
| 6 |
≈1163.167;
小数点后第1个数字是1.
故选:D.
练习册系列答案
相关题目