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Answers
Solution :
[ SECTION A ]
- Define improper fraction and mixed fraction .
Answer :
Define an improper fraction to be a number of the form p/q where p & q € I where p ≥ q .
p and q may or may not be in their lowest terms i.e , ( p, q ) = or ≠ 1 .
Examples of improper fractions are 3/2 , 9/7 , etc .
A mixed fraction refers to the combination of a whole number and a fraction .
Example : 1 ¾ is a mixed fraction .
Conversion from improper fraction to mixed fraction :
Let the fraction be p/q , p > q and (p,q) ≠ 1 .
Let p = q k + c , where k and c are both constants , k & c ≥ 1 .
Fraction becomes :
→ ( qk + c )/q
→ k + (c/q)
→ k (c/q) .
This , k (c/q) is the mixed fraction . Expanding this , multiply k with the q and add c , divided all over by q .
2. Change the following improper fraction into mixed fraction :
- 15/4 & 98/9
Answer :
In the fraction, 15/4 , the numerator is 15 . This can be expressed as 4 × 3 + 3 .
So , the mixed fraction becomes 3 ¾ .
For 98/9 , the numerator here is 98 .
This can be written as :
98 = 9 × 10 + 8 .
So , the mixed fraction becomes :
10 ⁸/9 .
3. Reduce the given fractions into its lowest terms :
- 21/49 & 30/65
Answer :
For 21/49 , we can clearly notice that there is a multiple of 7 in both the numerator and denominator .
Cancelling it ;
=> 3/7 .
This is the required fraction in its lowest terms .
For 30/65 , we can clearly notice that there is a multiple of 5 in both the numerator and denominator .
Cancelling it ;
=>6/13 .
This is the required fraction in its lowest terms .
4. Which fraction is greater :
- 3/5 or 4/7 • 2/5 or 4/9
Answer :
3/5
= 3 × 7 / 5 × 7
= 21/35
4/7
= 4 × 5/ 7 × 5
= 20/35
21/35 > 20/35 .
So, 3/5 > 4/7 .
2/5
= 2 × 9/ 5 × 9 =
18/45
4/9
=> 4 × 5/ 9 × 5
=> 20/45
Now , 20/45 > 18/45
So, 4/9 > 2/5 .
5. Add the following :
- ¾ & 2/3. • 3/7 & 5/4
Answer :
The LCM of 3 and 4 is 12 .
3/4 + 2/3
=> [ 3 × 3 ] + [ 2 × 4 ] / 12
=> [ 9 + 8 ]/12
=> 17/12
=> 1 ⁵/12 ( answer )
The LCM of 4 and 7 is 28 .
3/7 + 5/4
=> [ 3 × 4 ] + [ 5 × 7 ]/28
=> ( 12 + 35 )/28
=> 47/28
=> 1 19/28 ( answer ) .
6. Subtract the following :
- 1/7 - 3/4 • 2/11 - 1/5
Answer :
1/7 - 3/4
=> [ 1 × 4 ] - [ 3 × 7 ]/12
=> { 4 - 21 }/12
=> - 17/ 12
=> - 1 5/12
2/11 - 1/5
=> [ 2 × 5 ] - [ 1 × 11 ]/55
=> { 10 - 11 }/55
=> -1 / 55 .
___________________________
Solution :
[ SECtion A CONTINUED ]
7. Two supplementary angles are in the ratio 4 : 5 . Find the angles .
Answer :
The supplementary angles are in the ratio 4 : 5 .
Let us assume that these angles are 4k and 5k respectively where k is any arbitrary constant > 1 .
Now, we know that , supplementary angles always add up to 180° .
So,
4k + 5k = 180°
=> 9k = 180°
=> k = 20°
Angle 1 = 4k = 4 × 20° = 80°
Angle 2 = 5k = 5 × 20° = 100°
Verification : Angle 1 + Angle 2 = 80° + 100° = 180°
Hence Verified
8. Two complementary angles are in the ratio 2 : 3 . Find the angles .
Answer :
The supplementary angles are in the ratio 2 : 3 .
Let us assume that these angles are 2k and 3k respectively where k is any arbitrary constant > 1 .
Now, we know that , complementary angles always add up to 90° .
So,
2k + 3k = 90°
=> 5k = 90°
=> k = 18°
Angle 1 = 2k = 2 × 18° = 36°
Angle 2 = 4k = 3 × 18° = 54°
Verification : Angle 1 + Angle 2 = 36° + 54° = 90°
Hence Verified
9. The measure of two complementary angles are (3x + 8) and (4x -2) . Find x .
Answer :
Here , the complementary angles are ( 3x + 8 )° and ( 4x - 2 ) ° respectively.
Complementary angles add up to 90°
→ ( 3x + 8 ) + (4x - 2 ) = 90°
→ 7x + 6 = 90°
→ 7x = 84°
→ x = 12°
Angle 1 = 3x + 8 = 36 + 8 = 44°
Angle 2 = 46°
Verification : Angle 1 + Angle 2 = 44° + 46° = 90°
10. Find the value of the angle if it's supplementary angle is ⅔ times is it .
Answer :
Let us assume that the required angle is x .
So , the supplementary angle becomes ⅔ x .
Supplementary angles add up to 180°
→ x + ⅔ x = 180°
→ 5/3 x = 180°
→ x = 108°
→ ⅔ x = 72°
Thus , the required angle is 108°
______________________
Section B :
1. In the adjoining figure , find the value of a and b if a : b = 4 : 5 .
Answer :
Here , a : b = 4 : 5 .
Let a and b be 4x and 5x respectively .
From the figure , it is clear that a and b are supplementary angles .
So ,
a + b = 180°
=> 4x + 5x = 180°
=> 9x = 180°
=> x = 20°
a = 4x = 80°
b = 5x = 100°
Verification : a + b = 80° + 100° = 180°
2. Two complementary angles differ by 40°. Find the angles .
Answer :
Let the two complementary angles be x and y respectively .
As per the data given ;
x - y = 40° ......... (1)
Also ,
x + y = 90° ........... (2)
Adding both the equations ;
2x = 130°
=> x = 65°
y = 25° .
Thus , x and y are 65° and 25° respectively .
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