Question 15 of 31intermediate🔧 ApplyShort Answer2 marks

What will be the digital root of the number 9a + 36b + 13?

Correct Answer

Given: Expression: 9a + 36b + 13

Step 1: 9a is a multiple of 9 Digital root of 9a = 9

Step 2: 36b = 9×49 \times 4b is a multiple of 9 Digital root of 36b = 9

Step 3: Digital root of 13 = 1 + 3 = 4

Step 4: Digital root of (9a + 36b + 13) = Digital root of (9 + 9 + 4) = Digital root of 22 = 2 + 2 = 4

Answer: The digital root of 9a + 36b + 13 is 4.

Exercise: Figure it Out (Section 3) | Q: 3 | (Page Page 20)
For More Understanding

Explanation

The chapter explains that the digital root of any multiple of 9 is 9. Since 9a is a multiple of 9, its digital root is 9. Similarly, 36b = 9×49 \times 4b is also a multiple of 9, so its digital root is 9. The digital root of 13 is 1 + 3 = 4. Therefore, digital root of (9a + 36b + 13) = digital root of (9 + 9 + 4) = digital root of 22 = 2 + 2 = 4.

Solution Steps

  1. 9a is a multiple of 9, digital root = 9

  2. 36b = 9×49 \times 4b is a multiple of 9, digital root = 9

  3. Digital root of 13 = 1 + 3 = 4

  4. Digital root of sum = digital root of (9 + 9 + 4) = digital root of 22 = 4

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