SAT数学题啊各种求解释和解答 3,8,18……In the sequence above, the first term is 3 and each term after the first term is twice the sum of the preceding term and 1. For example, 8=2(3+1). What is the value of the first term of sequence th

Question

SAT数学题啊各种求解释和解答

  3,8,18……

In the sequence above, the first term is 3 and each term after the first term is twice the sum of the preceding term and 1. For example, 8=2(3+1). What is the value of the first term of sequence that is greater than 100?

To get the most benefit from exercise, it is recommended that a person attain a heart rate, measured in beats per minute, that is between 60 percent and 75 percent of the value obtained by subtracting the person's age from 220. What is one possible heart rate, in beats per minute, recommended for a 20-year-old jogger?

When a certain two-digit number is multiplied by a certain one-digit number, the product is 891. If the one-digit number is subtracted from two-digit number, what is the result?

a<b<c<d<e

p=abcde 

In the inequality and the equation above, a, b, c, d, and e are positive integers. When just one of these integers is increased by 1 and multiplied by the other four, the new product is n. The difference (n-p) is  greatest when which of the five integers is increased by 1?

Answer 1

1） 3,8,18……
In the sequence above,the first term is 3 and each
term after the first term is twice the sum of the preceding term and 1.
For example,8=2(3+1).What is the value of the first term of sequence
that is greater than 100?
翻译：在上述序列中,第一个数字是3,之后每一个数字是它之前的数字加上1后的和的2倍,比如8=2(3+1).那么整个序列大于100的数字中第一个数字是多少?
解析：按照序列规则,可以陆续写出后续数字依次为：
1、3、8、18、38、78、158、318...
可见,答案是158.
2）To
get the most benefit from exercise,it is recommended that a person
attain a heart rate,measured in beats per minute,that is between 60
percent and 75 percent of the value obtained by subtracting the person's
age from 220.What is one possible heart rate,in beats per minute,
recommended for a 20-year-old jogger?
翻译：为了达到最好的锻炼效果,推荐衡量锻炼者每分钟达到的心跳数,心跳数要到达220减去年龄的60%-75%期间.那么对于年龄20岁的慢跑者,每分钟达到的心跳值是什么范围?
答案：（220-20)*60%=120 (220-20)*75%=150,则应该是120-150次/每分钟.
3）When
a certain two-digit number is multiplied by a certain one-digit number,
the product is 891.If the one-digit number is subtracted from
two-digit number,what is the result?
翻译：当某2位数和某1位数相乘,积是891.如果这个2位数减去这个1位数,结果是多少?
分析：891,尾数为1,那么只能是两个尾数分别是3、7或者9、9的数字相乘的结果.
如果那个个位数是3,另一位是297（三位数,不符）,如果那个个位数是7,无法整除,不符.所以那个个位数只能是9,另一位是99,是两位数,符合题意.则两个数字分别是99和9.
答案：90 （99-9）
4）a