RATIO PROPORTION INDICES AND LOGARITHMS CA FOUNDATION QUESTIONS

Problem 1 :

In 40 litres mixture of glycerine and water, the ratio of glycerine and water is 3 : 1. The quantity of water added in the mixture in order to make this ratio 2 : 1 is

(a) 15 litres    (b) 10 litres        (c) 8 litres     (d) 5 litres

Solution:

The ratio of glycerine to water = 3 : 1

New ratio = 2 : 1

New ratio=Quantity of glycerineQuantity of water+x21=3010+x2(10+x)=3020+2x=302x=10x=102x=5 litres

So, option (d) is correct.

Problem 2 :

pa-b × pb-c × pc-a is equal to

(a) p                (b) 1           (c) 0         (d) none of these

Solution:

= pa-b × pb-c × pc-a

= pa-b+b-c+c-a

= p0

= 1

So, option (b) is correct.

Problem 3 :

If log mn+log nm=log(m+n) then

(a) m + n = 1     (b) m/n = 1      (c) m - n = 1    (d) m2 - n2 = 1

Solution:

log m+log n=log mnlog(m+n)=logmn×nmm+n=1

So, option (a) is correct.

Problem 4 : 

The compounded into of 4 : 9, the duplicate ratio of 3 : 4, the triplicate ratio of 2 : 3 and sub duplicate ratio of 9 : 64 is

(a) 2 : 7      (b) 7 : 2      (c) 1 : 36        (d) none of these

Solution:

Duplicate of ratio 3:4=3242=9:16Triplicate of ratio 2:3=2333=8:27

Now, we have 4 ratios:

49,916,827 and964Compounded ratio of these ratios=4×9×8×99×16×27×64=196=1:96

So, option (d) is correct.

Problem 5 :

If 2x - 2x-1 = 32, then the value of x is

(a) 4     (b) 5     (c) 6     (d) 7

Solution:

2x-2x-1=32Let 2x=uu-2-1×u=32u-12u=3212u=32u=642x=26x=6

So, option (c) is correct.

Problem 6 :

The integral part of a logarithm is called _____, and the decimal part of a logarithm is called _____.

(a) Mantissa, Characteristic       (b) Characteristic, Mantissa

(c) Whole, Decimal         (d) None of these

Solution:

The integral part of a logarithm is called Characteristic, and the decimal part of a logarithm is called Mantissa.

So, option (b) is correct.

Problem 7 :

Given log 2 = 0.3010 and log 3 = 0.4771 then the value of log 24

(a) 1.3081     (b) 1.1038     (c) 1.3801      (d) 1.8301

Solution:

We know that,

log(ab) = log a + log b

Therefore, log 24 = log(2 x 2 x 2 x 3)

= log 2 + log 2 + log 2 + log 3

= 0.3010 + 0.3010 + 0.3010 + 0.4771

= 1.3801

So, option (c) is correct.

Problem 8 :

If a=32+1-32-1 then the value of a3+3a-2 is

(a) 3    (b) 0      (c) 2      (d) 1

Solution:

a=32+1-32-1Cubing both sides, we get a3=32+1-32-13a3=2+1-2+1-3×32+1×32-132+1-32-1a3=2-3×32-1aa3=2-3aa3+3a-2=0

So, option (b) is correct.

Problem 9 :

In a ratio, which is equal to 3 : 4, if the antecedent is 12, then the consequent is :

(a) 9      (b) 16       (c) 20        (d) 24

Solution:

34=12x3x=12×43x=48x=483x=16

So, option (b) is correct.

Problem 10 :

The simplification of log2 16 8+log5 425625 is

(a) 2         (b) 3          (c) 4         (d) 6

Solution:

=log2 16 8+log5 425625=log2 24 22+log5521/454=log22521/2+log5(5)1/2-log5(5)4=log22112+log551/25-4=112log2 2+log55-7/2=112(1)+-72log55=112-72=42=2

So, option (a) is correct.

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