Question

If a . b = 7:9 and b
c
= 5:7, then find the value of a
C?
(A) 7:21
(B) 7:15
(C) 5:9
(D) 3:5​

Answer 1

Answer:

$\huge{\red{Hola Mate}}$

Here is the Answer........

a:b=7:9

and

b:c=5:7

Now , Here b is common in both terms.

Thus,take LCM of b and that is 9×5=45.

Now, in 1st ratio , 9×5 =45 ,

Thus multiply whole term by 5....

Now , 1st ratio ==35:45

Repeat the same in 2nd ratio...

We get 5×9=45...

Thus, 2nd ratio=45:63

Now we are done...

Combine both the ratios....

We get 35:45:63

We need only a:c...

Thus 35:63

Which is equal to ==>>

$\huge{\red{<strong><em>5</em></strong><strong><em>:</em></strong><strong><em>9</em></strong>}}$

..............................-------------------.....................

Hope this Helps....

Answer 2

Answer:

a : c = 5 : 9

The answer is Option (C)  5 : 9

Step-by-step explanation:

Given :

a : b = 7 : 9

b : c = 5 : 7

To Find :

The Value of a : c

Solution :

The Corresponding Fraction of a : b and b : c = $\sf{\dfrac{7}{9} \:and\: \dfrac{5}{7}}$

As 'b' is common in both the fractions, make them equal.

LCM of 9 and 5 = 45

⇒ $\sf{\dfrac{7 \times 5}{9 \times 5}\:\:\:\:\:\:\dfrac{5 \times 9}{7 \times 9}}$

⇒ $\sf{\dfrac{35}{45}\:\:\:\:\:\:\dfrac{45}{63}}$

a : b = 35 : 45

b : c = 45 : 63

$\rule{300}{1}$

a : c = 35 : 63 = $\dfrac{35}{63}$

⇒ $\dfrac{35}{63}$

⇒ $\dfrac{5}{9}$

⇒ a : c =  $\dfrac{5}{9}$

∴ The answer is Option (C)  5 : 9