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Word of the Day
languid
Definition: (adjective) without energy; slow, sluggish, listless.
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Math Teaser
Problem
A palindrome is a positive integer that reads the same forward as it does backwards. If neither the first nor last digit of a palindrome can be zero, how many three-digit palindromes are there?
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SAT* Tip of the Day
So What?
All lines either intersect or are parallel.
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SAT: Grid-In Question #7

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Question: When a test is administered to 8 students, the average (arithmetic mean) of the scores is 85. If 2 more students take the test and receive scores of 90 and 100, what is the average score of all the test takers?


 Remember that the average   = 
 sum of terms 
 number of terms 
 . 
  
 In the original group of test takers, the average score is 85 and  
 the number of test takers is 8, so you can plug in these numbers 
 to solve for the sum of the scores.  
  
 You have  85  = 
 sum of scores 
8
 , and the sum of the scores   = 
85  ×  8  =  680  . 
  
 When 2 more students take the test, they receive scores of 
  90 and 100. So the new sum of the scores is: 
680  +  90  +  100  =  870  , and the new number of test takers is: 
8  +  2  =  10.
  
 Substituting these values into the average formula, you have that: 
  the average   = 
870
10
 =  87  . Hence, the average score of all the  
 test takers is 87. 


 

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