Kerala Syllabus Class 5 Mathematics - Unit 2 Number World - Questions and Answers | Teaching Manual 


Questions and Answers for Class 5 Mathematics - Unit 2 Number World - Study Notes | Text Books Solution STD 5 - Maths: Unit 2 Number World - Questions and Answers | സംഖ്യാലോകം  

അഞ്ചാം ക്ലാസ്സ്‌  Mathematics - Unit 2 Number Wprld  എന്ന പാഠം ആസ്പദമാക്കി തയ്യാറാക്കിയ ചോദ്യോത്തരങ്ങള്‍. ഈ അധ്യായത്തിന്റെ Teachers Handbook, Teaching Manual എന്നിവ ഡൗൺലോഡ് ചെയ്യാനുള്ള ലിങ്ക് ചോദ്യോത്തരങ്ങളുടെ അവസാനം നൽകിയിട്ടുണ്ട്.

STD 5 - Maths: Unit 2 Number World - Questions and Answers

♦ Textbook Activities - Page 28
1.  How many two-digit numbers are there with 0? How many without 0?
Answer:
Number of two-digit numbers with '0' = 9 
(10, 20, 30, 40, 50, 60, 70, 80, 90) 
Total number of two-digit numbers = 90 
Number of two-digit numbers without '0' = 90 - 9 = 81

2 How many three-digit numbers are possible with two 0?
ii. How many three-digit numbers are there with only one 0?
iii. How many three-digit numbers are there without any zero?
Answer:
i. Number of three-digit numbers with two 0 = 9
(100, 200, 300, 400, 500, 600, 700, 800, 900) 

ii. Number of three-digit numbers with only one 0. 
From 100 to 199 we have 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 120, 130, 140, 150, 160, 170, 180, 190
Total 18 numbers. Like this if we consider up to 999, total number of three-digit number with only one 0 = 18x9 = 162

iii. Total number of three-digit numbers = 900
Out of the total 900 three-digit numbers, 162 are with one zero only, 9 are with two zeros, so subtracting these from 900 we get the answer 900-(162+9)
any zero
Total number of three-digit numbers without 900-(162+9)=900-171 = 729 

3. How many two-digit numbers are there with the same digit repeated? How many three-digit numbers with the same digit repeated thrice?
Answer:
Number of two-digit numbers with the same digit repeated = 9
(11, 22, 33, 44, 55, 66, 77, 88, 99)
Three-digit numbers with the same digit repeated = 9
(111, 222, 333, 444, 555, 666, 777, 888, 999) 
4. There are some numbers which read the same when the digits are put in the reverse order. For example, 46764. Such numbers are called palindromic numbers.
i. How many two-digit numbers are palindromes?
II. How many three-digit numbers?
iii. Four-digit numbers?
Answer:
i. Number of two-digit palindromic numbers = 9
(11, 22, 33, 44, 55, 66, 77, 88, 99)

ii. From 100 to 199.
(101,111,121,131,141,151,161,171,181,191)
Total number = 10
Like this, if we consider up to 999 Number of three-digit palindromic numbers = 10 x 9=90
90 three-digit numbers are palindromic

iii. From 1000 to 1999.
(1001, 1111, 1221, 1331, 1441, 1551, 1661, 1771, 1881, 1991)
Like this, if we consider up to 9999 
Number of four-digit palindromic numbers = 10 x 9=900
90 four-digit numbers are palindromic 

5. How many four-digit numbers can be made using all the digits 1, 2, 3, 4? What is the sum of all these?
Answer:
Number of four-digit numbers formed using the digits 1, 2, 3, 4 = 4×3×2×1=24
In each place, 1, 2, 3, 4 must occur equally often, so that in each place there are six numbers
6+12+18+ 24 = 60
So, 60 ones + 60 tens + 60 hundreds + 60 thousands
That is 60+ 600+ 6000+ 60000 = 66660

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