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Hi, I am confused on this question:


The sequence 12, 15, 18, 21, 51, 81, ... consists of all positive multiples of 3 that contain at least one digit that is a 1. What is the 50th term of the sequence?


(Source: 2006 National Target #5)

Respuesta :

oscar236

Answer:

321.

Step-by-step explanation:

The next term after 81 is 102 .

Between  102 and 198 inclusive we have  (198-102)  / 5  + 1 = 96/3 + 1 = 33 terms - these will all have at least one 1 and be divisible by 3.

So 198 = 6 + 33 = 39th term.

After 198 we have 201, 210, 213, 219, 231, 261, 291, 312, 315, 318, 321

The answer is 321..

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