<p>Hi everyone, I can't believe I'm not understanding this problem! The answer is 8, but I'm not sure I comprehend why.</p>
<p>"There is the same number of boys and girls on a school bus when it departs from school. At the first stop, 4 boys get off the bus and nobody gets on. After the first stop, there are twice as many girls as boys on the bus. How many girls are on the bus?"</p>
<p>I've been trying to set it up algebraically, but it's not working too well...</p>
<p>b = g</p>
<p>then...</p>
<p>b - 4 = 2g</p>
<p>but it's impossible to solve with two variables!</p>
<p>“At the first stop, 4 boys get off the bus and nobody gets on. After the first stop, there are twice as many girls as boys on the bus.”</p>
<p>If you just do it in your head 8 is the obvious number (4 * 2 = …). And you set up the equation wrong. It should be b - 4 = g/2 and 8 is the only number that fits so… </p>
<p>Hopefully you’re getting the other #1’s right. xD</p>
<p>ds143, you were really close but you put the 2 in the wrong place. At first, b=g because both are equal. But after 4 boys get off, now it is twice the number of boys that is equal to the number of girls. </p>
<p>b = g
then…
2*(b-4) = g
b-4 = .5g
b = .5g + 4</p>
<p>now plugging in .5g+4 for “b” in the original equation…
.5g+4=g
4 = g - .5g
4 = .5g
g = 8</p>
<p>Remember that “twice as many girls” does not always mean 2g. If there are twice as many girls as boys, that means there are more girls, so you are going to have to make the number of boys bigger, i.e. g = 2b. The bigness of the girls is already built into the letter g, so you don’t need to make it twice as big again. You have to make the b, which is half the size as g, bigger.</p>