Gmat数学题:How many integers between 1 and 100,inclusive,can be divided by none of 2,3,and
来源:学生作业帮助网 编辑:六六作业网 时间:2024/12/26 03:13:51
Gmat数学题:How many integers between 1 and 100,inclusive,can be divided by none of 2,3,and
Gmat数学题:How many integers between 1 and 100,inclusive,can be divided by none of 2,3,and
Gmat数学题:How many integers between 1 and 100,inclusive,can be divided by none of 2,3,and
1到100 共100个数,
偶数能被2整除,有50个,扣掉
被5整除的找尾数是5 或10 就行,这里找尾数是5的(尾数是10的已经算在偶数内)有10个
被3整除的情况,每30一个周期,如 3 9 21 27; 33 39 51 57,发现规律没有?
所以是3*4+2=14个(最后两个是93和99)
所有情况是 100-50-10-14=26个
把能整除2,3,5的找出来,排除可得。
100/2=50, half of the numbers out
100/3=33...1, and every one out of two can also be divided by 2, so 33-16=17
100/5=20, and every four out of six can be divided by eit...
全部展开
把能整除2,3,5的找出来,排除可得。
100/2=50, half of the numbers out
100/3=33...1, and every one out of two can also be divided by 2, so 33-16=17
100/5=20, and every four out of six can be divided by either 2 or 3, so we have 18/3=6
the number of integers that can be divided by 2,3 or 5 is 50+17+7=74
so the answer is 100-74=26
收起
,25个,分别是1,7,11,13,17,19,23,29,31,37,41,43,47,49,51,53,59,61,67,71,73,77,79,83,89,91,97,
gmat数学考试的话你可以看看管卫东老师的gmat数学笔记,他讲的很不错,管卫东团队博客就有的
可以使用 venn diagram来解答。画三个圆,一个圆是2的倍数,一个圆是3的倍数,一个圆是5的倍数。求2,3,5在100内一共多少倍数可以用一下公式来表示:
y= A+B+C-D-E-F+G
=50+33+20-16-10-6+3=74
A: 2的倍数个数=100/2=50
B: 3的倍数=100/3=33
C: 5的倍数=100/5=...
全部展开
可以使用 venn diagram来解答。画三个圆,一个圆是2的倍数,一个圆是3的倍数,一个圆是5的倍数。求2,3,5在100内一共多少倍数可以用一下公式来表示:
y= A+B+C-D-E-F+G
=50+33+20-16-10-6+3=74
A: 2的倍数个数=100/2=50
B: 3的倍数=100/3=33
C: 5的倍数=100/5=20
D: 2*3的倍数=100/(2×3)=100/6=16
E: 2*5倍数=100/10=10
F: 3*5的倍数=100/15=6
G: 2*3*5的倍数也就是30的倍数=100/30=3
所以,100内不是2,3,5的倍数有100-74=26
这种解题思路的好处显而易见,可以套公式,因此不容易出错。
收起