RATIO PROPORTION INDICES AND LOGARITHMS CA FOUNDATION TEST

Problem 1 :

Calculate the duplicate ratio of x4:y5.

(a) 4x2 : 5y2    (b) 16x2 : 25y2    (c) 25x2 : 16y2

(d) none of these

Solution:

Duplicate ratio of ab=a2b2=x242:y252=x216:y225=25x2:16y2

So, option (c) is correct.

Problem 2 :

If A3=B4=C5, then 2A+B+CC is

(a) 2    (b) 3    (c) 5    (d) 6

Solution:

A3=B4=C5 A3=C5A=3C5B4=C5B=4C52A+B+CC=23C5+4C5+CC=6C5+4C5+CC=C65+45+1C=65+45+1=6+4+55=1552A+B+CC=3

So, option (b) is correct.

Problem 3 :

If a1/3 + b1/3 + c1/3 = 0 then the value of (a + b + c)3 is 

(a) abc    (b) 9bac      (c) 27abc     (d) 1/27abc

Solution:

Given a13+b13+c13=0Using identity a3+b3+c3=3abcHere a=a13,b=b13,c=c13a133+b133+c133=3×a13×b13×c133a3+(3b)3+(3c)3=3×3a×3b×3ca+b+c=3×3a×3b×3cTaking cube on both sides we get,(a+b+c)3=3×3a×3b×3c3(a+b+c)3=27abc

So, option (c) is correct.

Problem 4 :

The value of 1loga(ab)+1logb(ab) is

(a) 0      (b) 1      (c) -1       (d) None

Solution:

1loga(ab)+1logb(ab)log ab=log a + log b=1loga(ab)+1logb(ab)=1log(ab)log a+1log(ab)log b=log alog ab+log blog ab=log a+log blog ab=log ablog ab=1

So, option (b) is correct.

Problem 5 :

If 8n×23×(16)-12n×42=14, then the value of n is

(a) 3         (b) 3/2        (c) 1          (d) 2/3

Solution:

8n×23×(16)-12n×42=1423n×23×2-42n×24=142(3n+3-4)2(n+4)=1423n-12n+4=1423n-1-n-4=1422n-5=2-22n-5=-22n=-2+52n=3n=32

So, option (b) is correct.

Problem 6 :

Ratio between 25 hours and 45 minutes is

(a) 5 : 9           (b) 100 : 3       (c) cannot be determined

(d) None

Solution:

1 hour = 60 minutes

25 hours = 60 × 25

= 1500 minutes

Ratio of 1500 minutes and 45 minutes is

= 1500 : 45

= 100 : 3

So, option (b) is correct.

Problem 7 :

The logarithm of 21952 to the base of 2√7 and 19683 to the base of 3√3 are

(a) Equal      (b) Not equal       (c) have a difference of 2269

(d) None

Solution:

=log27(21952)=log2726×73=log2726×76=log27276=6 log2727=6
=log33(19683)=log3339=log3336×33=log3336×36=log33336=6 log3333=6

So, option (a) is correct.

Problem 8 :

If ab=43 and xy=75 then, find 2ax-3byax+by.

(a) 116 : 31     (b) 19 : 37      (c) 11 : 43     (d) 18 : 35

Solution:

Given, a  = 4, b = 3 and x = 7, y = 5

2ax-3byax+by=2(4)(7)-3(3)(5)(4)(7)+(3)(5)=56-4528+15=1143Ratio = 11:43

So, option (c) is correct.

Problem 9 :

If 2x × 3y × 5z = 360 Then what is the value of x, y, z ?

(a) 3, 2, 1     (b) 1, 2, 3      (c) 2, 3, 1     (d) 1, 3, 2

Solution:

2x × 3y × 5z = 360

2x × 3y × 5z = 36 × 10

= 2 × 2 × 3 × 5 × 2

So, 2x × 3y × 5z = 23 × 32 × 51

x = 3, y = 2, z = 1

So, option (a) is correct.

Problem 10 :

255÷2510is equal to (a) 255(b) 525(c) 3225(d) 62532

Solution:

=255÷2510=2555×510210=5525=525

So, option (b) is correct.

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