Question

$20$ 枚二十五美分硬币和 $10$ 枚十美分硬币的总价值，等于 $10$ 枚二十五美分硬币和 $n$ 枚十美分硬币的总价值。 $n$ 是多少？

The value of $20$ quarters and $10$ dimes equals the value of $10$ quarters and $n$ dimes. What is $n?$

$10$

$20$

$30$

$35$

$45$

先求 $20$ 枚二十五美分硬币和 $10$ 枚十美分硬币的总价值

First find the total value of $20$ quarters and $10$ dimes

去掉 $10$ 枚二十五美分硬币的价值后，剩下的价值都要由 $10$ 美分硬币补足

After using $10$ quarters, find how much value the remaining dimes must supply, then divide by $10$ ¢

$20$ 枚二十五美分硬币和 $10$ 枚十美分硬币的总价值是 $\$5.00 + \$1.00 = \$6.00$ 。

十枚二十五美分硬币值 $\$2.50$ ，所以 $n$ 枚十美分硬币必须值 $\$6.00 - \$2.50 = \$3.50$ 。这相当于 $35$ 枚十美分硬币，因此 $n = 35$ 。

所以正确答案是 D。

The value of $20$ quarters and $10$ dimes is $\$5.00 + \$1.00 = \$6.00.$

Ten quarters are worth $\$2.50,$ so the $n$ dimes must supply $\$6.00 - \$2.50 = \$3.50.$ That is $35$ dimes, so $n = 35.$

Thus, the correct answer is D .