Solve the following riddle: I am a number, Tell my identity! Take me seven times over, And add a fifty! To reach a triple century, You still need forty!

Let the number be n.
According to the question, 7n + 50 + 40 = 300
⇒ 7n+90 = 300
⇒ 7n = 300-90
⇒ 7n = 210
⇒ 7n = 210/7
⇒ n = 30
Thus, the required number is 30.

Class 7 Maths Chapter 4 Exercise 4.4

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