Large Numbers in Practice
we have learnt that we use centimetre (cm) as a unit of length. For measuring the length of a pencil, the width of a book or notebooks etc., we use centimetres. Our ruler has marks on each centimetre. For measuring the thickness of a pencil, however, we find centimetre too big. We use millimetre (mm) to show the thickness of a pencil.
(a)    10 millimetres = 1 centimetre
To measure the length of the classroom or  the school building, we shall find centimetre too small. We use metre for the purpose.
(b)    1 metre = 100 centimetres = 1000 millimetres
Even metre is too small, when we have to state distances between cities, say, Delhi and Mumbai, or Chennai and Kolkata. For this we need kilometres (km).

We have done a lot of problems that have addition, subtraction, multiplication and division.
We will try solving some more here.

Ex :    Population of Sundarnagar was 2,35,471 in the year 1991. In the year 2001 it was found to be increased by 72,958. What was the population of the city in 2001?
Sol.    Population of the city in 2001   = Population of the city in 1991 + Increase in population
= 2,35,471 + 72,958
Now,     235471
+ 72958
308429
Salma added them by writing 235471 as 200000 + 35000 + 471 and 72958 as 72000 + 958.
She got the addition as 200000 + 107000 + 1429 = 308429.
Mary added it as 200000 + 35000 + 400 + 71 + 72000 + 900 + 58 = 308429
Answer : Population of the city in 2001 was 3,08,429.
All three methods are correct.

Ex:    In one state, the number of bicycles sold in the year 2002-2003 was 7,43,000. In the year 2003-2004, the number of bicycles sold was 8,00,100. In which year were more bicycles sold? and how many more?
Sol.     Clearly, 8,00,100 is more than 7,43,000. So, in that state, more  bicycles were sold in the year 2003-2004 than in 2002-2003.
Now,       800100
– 743000
057100