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Roman Numeral Hindu-Arabic Equivalent XL 40 = 50 - 10
IV 4 = 5 - 1 XC 90 = 100 - 10
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IX 9 = 10 - 1 CD 400 = 500 100
CM 900 = 1000 100
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5. To represent larger numbers, a bar over a numeral means to multiply the number by 1000.
For example, D represents 1000 ´ 500 = 500,000 and M represents 1000 ´ 1000 = 1,000,000,
(one million or ten lakh).

E xercise 1.3

1. Write the follow ing numbers using Roman Numer als:
(i) 47 (ii) 123 (iii) 1998 (iv) 2345
2. Write the follow ing numbers using Hindu-Arabic numer als:
(i) DCXLVIII (ii) MMDXLIX (iii) MCMXLIV (iv) MCMXCIX
3. What is the larg est number you can write in Roman numer als with out using bars?
4. Perform the follow ing arith me tic oper a tions. Can you do these with out convert ing the numbers to
usual nota tion?
(i) LXVI + XXXIV (ii) CXLVII + MCV (iii) XXXIV + LXV

Summary

1. Given two numbers, one with more digits is the greater number. If the number of digits in two given
numbers is the same, that number is greater, which has a greater leftmost digit.
If this digit also happens to be the same, we look at the next digit on the left and so on.
2. In form ing numbers from given digits, we should be care ful to see if the condi tions under which the
numbers are to be formed are satis fied.
3. The small est six digit number is 1,00,000. It is one lakh and follows the larg est five digit number 99,999.
This carries on for higher digit numbers in a simi lar manner.
4. Use of commas helps in read ing and writ ing large numbers.
5. Large numbers are needed in many ways in daily life.
6. Remem ber that kilo means 1000, Centi means 100th part and milli means 1000th part. Thus,
1 kilo metre = 1000 metres, 1 metre = 100 centi metres or 1000 milli metres etc.
7. There are a number of situ a tions in which we do not need the exact quan tity but need only a reason -
able guess or an esti mate.
8. Esti ma tion involves approx i mat ing a quan tity to an accu racy required.
9. In number of situations, we have to estimate the outcome of number oper ations. This is done by
round ing off the numbers involved and getting a quick, rough answer.
10. Many civilizations used other means to denote numbers. For example, the Romans represented
numbers using the numer als I, V, X, L, C, D, and M.

Review Exercise
Choose correct option in ques tions 1 to 5.

1. 123456 ____ 78945
(a) > (b) < (c) = (d) none of these
2. 15678 ____ 26754
(a) < (b) > (c) = (d) none of these
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Mathematics In Focus - 6