Kee Pang's answer to Shei Ling's Secondary 2 Maths Singapore question.
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Let the total number of students in this class be X.
Since each student will send a letter to every other student, each student will send (X - 1) letters.
The total number of letters send will tally as:
(X) (X - 1) = 870
X^2 - X = 870
X^2 - X - 870 = 0
(X - 30) (X + 29) = 0
X = 30 or X = -29 (Rejected as X cannot be negative)
Hence, there are 30 students in the class. [X^2 is X square]
Since each student will send a letter to every other student, each student will send (X - 1) letters.
The total number of letters send will tally as:
(X) (X - 1) = 870
X^2 - X = 870
X^2 - X - 870 = 0
(X - 30) (X + 29) = 0
X = 30 or X = -29 (Rejected as X cannot be negative)
Hence, there are 30 students in the class. [X^2 is X square]
Date Posted:
4 years ago
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