Answer:
Step-by-step explanation:
=7 (1+11+111+1111......n)
=7/9 (9+99+999+9999....n)
=7/9 ((10-1)+(10^2-1)+(10^3-1)+....n)
=7/9 ((10+10^2+10^3...n)-(1+1+1+1.....n))
=7/9 ((10 (10^n-1)/(10-1))-n)
3 x
---------= --------- ---------
15 180
15x=540
----- ------= 36 students.
15 15
Steps: Cross multiply to get 15x and 540. Divide both numbers by 15, then you found what x equals, which is the answer.
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