I*****n
发帖数: 90 | 1 A marching band is parading down Main Street at a constant
speed. The bass drum player has a dog that runs to the front
row and then back to its owner, going back and forth, also at a
constant speed. The distance between the back row and front
row of the marching band is 50 feet. In the time the dog went
back and forth, the bass drum player marched 50 feet. Find
the length of the dog’s path. |
u****s
发帖数: 161 | 2 drum players are always in the last row of a band?
【在 I*****n 的大作中提到】
: A marching band is parading down Main Street at a constant
: speed. The bass drum player has a dog that runs to the front
: row and then back to its owner, going back and forth, also at a
: constant speed. The distance between the back row and front
: row of the marching band is 50 feet. In the time the dog went
: back and forth, the bass drum player marched 50 feet. Find
: the length of the dog’s path.
|
d******e
发帖数: 299 | 3 isn't it 150 feet?
【在 I*****n 的大作中提到】
: A marching band is parading down Main Street at a constant
: speed. The bass drum player has a dog that runs to the front
: row and then back to its owner, going back and forth, also at a
: constant speed. The distance between the back row and front
: row of the marching band is 50 feet. In the time the dog went
: back and forth, the bass drum player marched 50 feet. Find
: the length of the dog’s path.
|
o*******n
发帖数: 6500 | 4 取决于drum player在队伍的哪个位置
以及最后停下来的时候，狗在队伍的哪个位置。。。
【在 I*****n 的大作中提到】
: A marching band is parading down Main Street at a constant
: speed. The bass drum player has a dog that runs to the front
: row and then back to its owner, going back and forth, also at a
: constant speed. The distance between the back row and front
: row of the marching band is 50 feet. In the time the dog went
: back and forth, the bass drum player marched 50 feet. Find
: the length of the dog’s path.
|
I*****n
发帖数: 90 | 5 这是人家给的答案, 谁给解释一下, 看了半天答案, 我还是没想明白到底drum player
在哪儿.
While this can be done with a little hit or miss arithmetic, algebra makes
it easier:
While the band went x feet ahead, the dog ran 50+x
While the band went 50-x dog ran x
so: x/(50+x)=(50-x)/x
==>x=35 |
I*****n
发帖数: 90 | 6 这是人家给的答案, 谁给解释一下, 看了半天答案, 我还是没想明白到底drum player
在哪儿.
While this can be done with a little hit or miss arithmetic, algebra makes
it easier:
While the band went x feet ahead, the dog ran 50+x
While the band went 50-x dog ran x
so: x/(50+x)=(50-x)/x
==>x=35 |
c*****g
发帖数: 1137 | 7 最后一排
player
【在 I*****n 的大作中提到】
: 这是人家给的答案, 谁给解释一下, 看了半天答案, 我还是没想明白到底drum player
: 在哪儿.
: While this can be done with a little hit or miss arithmetic, algebra makes
: it easier:
: While the band went x feet ahead, the dog ran 50+x
: While the band went 50-x dog ran x
: so: x/(50+x)=(50-x)/x
: ==>x=35
|
N*****N
发帖数: 1605 | 8 参见本版3376
【在 I*****n 的大作中提到】
: A marching band is parading down Main Street at a constant
: speed. The bass drum player has a dog that runs to the front
: row and then back to its owner, going back and forth, also at a
: constant speed. The distance between the back row and front
: row of the marching band is 50 feet. In the time the dog went
: back and forth, the bass drum player marched 50 feet. Find
: the length of the dog’s path.
|
h*****0
发帖数: 4889 | 9 haha, you make the most likely mistake in this problem.
【在 d******e 的大作中提到】
: isn't it 150 feet?
|
h*****0
发帖数: 4889 | 10 狗从最后跑到最前这一过程，队伍行进了x，狗走了50+x
然后狗跑回这过程，队伍行进了50-x，狗走了x
速度比不变，故得方程，解出x = 35
狗走的总路程是50+2x = 120
player
【在 I*****n 的大作中提到】
: 这是人家给的答案, 谁给解释一下, 看了半天答案, 我还是没想明白到底drum player
: 在哪儿.
: While this can be done with a little hit or miss arithmetic, algebra makes
: it easier:
: While the band went x feet ahead, the dog ran 50+x
: While the band went 50-x dog ran x
: so: x/(50+x)=(50-x)/x
: ==>x=35
|
