神马作文网猴哥112 中的第57题怎么做啊?求大神帮忙啊
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猴哥112 中的第57题怎么做啊?求大神帮忙啊
不好意思 错了 是58题 pdf版
不好意思 错了 是58题 pdf版
是下面这题么?貌似不应该难倒人吧?
Question 58:
How many four-digit numbers begin with an odd digit and end with an even digit?
a. 250
b. 500
c. 2,000
d. 2,500
e. 5,000
Solution: d
1. Only four-digit numbers beginning with 1, 3, 5, 7, and 9 satisfy the condition, i.e. 1xxx, 3xxx, 5xxx, 7xxx and 9xxx, and in each of the 5 groups there are 1000 numbers(-000 to -999).
2. Obviously, 50% of the 1000 numbers are odd and 50% even, as they appear in an alternating manner.
2. Therefore, 500X5=2500.
再问： 是那道上边的看图题，能帮我解释下那个2问什么错，和3问什么对吗？谢谢了回复
Question 58:
How many four-digit numbers begin with an odd digit and end with an even digit?
a. 250
b. 500
c. 2,000
d. 2,500
e. 5,000
Solution: d
1. Only four-digit numbers beginning with 1, 3, 5, 7, and 9 satisfy the condition, i.e. 1xxx, 3xxx, 5xxx, 7xxx and 9xxx, and in each of the 5 groups there are 1000 numbers(-000 to -999).
2. Obviously, 50% of the 1000 numbers are odd and 50% even, as they appear in an alternating manner.
2. Therefore, 500X5=2500.
再问： 是那道上边的看图题，能帮我解释下那个2问什么错，和3问什么对吗？谢谢了回复