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If 31z5 is a Multiple of 9, Where Z Is a Digit, What is the Value Of Z? You Will Find that There Are Two Answers for the Last Problem. Why is this So? - Mathematics

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प्रश्न

If 31z5 is a multiple of 9, where z is a digit, what is the value of z? You will find that there are two answers for the last problem. Why is this so?

उत्तर

If a number is a multiple of 9, then the sum of its digits will be divisible by 9.

Sum of digits of 31z5 = 3 + 1 + z + 5 = 9 + z

Hence, 9 + z should be a multiple of 9.

This is possible when 9 + z is any one of these numbers 0, 9, 18, 27, and so on …

However, since z is a single digit number, this sum can be either 9 or 18. Therefore, z should be either 0 or 9.

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अध्याय 16: Playing with Numbers - Exercise 16.2 [पृष्ठ २६०]

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एनसीईआरटी Mathematics [English] Class 8
अध्याय 16 Playing with Numbers
Exercise 16.2 | Q 2 | पृष्ठ २६०
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