Question 3 - Figure it out - Page 181 - Chapter 7 Class 7 - Finding the Unknown (Ganita Prakash II)

Transcript

Question 3 I am a 3-digit number. My hundred’s digit is 3 less than my ten’s digit. My ten’s digit is 3 less than my unit’s digit. The sum of all the three digits is 15. Who am I?A 3 digit number is like Let Unit’s digit be u Given that Ten’s digit is 3 less than my unit’s digit So, we can write Ten’s digit = Unit’s digit – 3 = u – 3 Also, given that hundred’s digit is 3 less than my ten’s digit Hundred’s digit = Ten’s digit – 3 = (u – 3) – 3 = u – 3 – 3 = u – (3 + 3) = u – 6 Finally, we are also given Sum of all the three digits is 15 So, we can write Hundred’s digit + Ten’s digit = Unit’s digit = 15 Putting values (u – 6) + (u – 3) + u = 15 u + u + u – 6 – 3 = 15 (u + u + u) – (6 + 3) = 15 3u – 9 = 15 Taking –9 left side, it becomes + 9 3u = 15 + 9 3u = 24 Taking 3 left side, so it becomes division u = 24/3 u = 8 Thus, Unit’s digit = u = 8 Ten’s digit = u – 3 = 8 – 3 = 5 Ten’s digit = u – 6 = 8 – 6 = 2 Thus, our 3 digit number is 258