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If a,b,ca, b, c are three positive integers such that a and b are in the ratio 3:43 : 4 while bb and cc are in the ratio 2:12:1, then which one of the following is a possible value of (a+b+c)(a + b + c)?

Solution

✅ Correct Option: 3

We have three positive integers aa, bb, cc with ratios a:b=3:4a : b = 3 : 4 and b:c=2:1b : c = 2 : 1.


From a:b=3:4a : b = 3 : 4, we get a=3ka = 3k and b=4kb = 4k for some positive integer kk.

From b:c=2:1b : c = 2 : 1, we get b=2mb = 2m and c=mc = m for some positive integer mm.


Since both expressions represent bb:

4k=2m4k = 2m

m=2km = 2k


Substituting back:

a=3ka = 3k

b=4kb = 4k

c=m=2kc = m = 2k


Therefore:

a+b+c=3k+4k+2k=9ka + b + c = 3k + 4k + 2k = 9k

Since kk must be a positive integer, possible values are 9,18,27,36,...9, 18, 27, 36, ...


For 207207:

9k=2079k = 207

k=23k = 23

This gives a=69a = 69, b=92b = 92, c=46c = 46.

Verification: 69:92=3:469:92 = 3:4 and 92:46=2:192:46 = 2:1 ✓

Therefore, 207207 is a possible value of (a+b+c)(a + b + c).

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