(a) Show that n^2 - n - 90 = 0
汉娜的糖
包里有n个糖。
其中有6个是橙色的。
其余的是黄色的。
汉娜随机从包里拿了一个糖。
吃了。
汉娜又随机从包里拿了一个糖。
吃了。
汉娜吃到两个橙色糖的可能性为三分之一
求证:n^2 - n - 90 = 0
Solution:
Take the words from the question, and write it down as an equation - 6/n x 5/(n-1) = 1/3
Multiply the 6 by the 5 and the n by the n-1. That gives you: 30/(n^2 - n) = 1/3
Multiply the top-left by bottom-right and top-right by bottom-left
Subtract 90 from both sides, leading to your answer n^2 - n - 90 = 0
解:
将题目中的表述列成等式:6/n x 5/(n-1) = 1/3
左边两项相乘的结果为:30/(n^2 - n) = 1/3
等式两边的分子与分母分别相乘得出:n^2 - n =90
两边各减去90得出:n^2 - n - 90 = 0
Use the repeated addition strategy to solve 5X3
5X3=?
用重复加法来计算5X3
错误答案:5+5+5
正确答案:3+3+3+3+3
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