Home › RRB NTPC › Quantitative Aptitude › Ratio and Proportion › If a : b = 2 : 3 and b : c = 4 : 5, then a : c e…
If a : b = 2 : 3 and b : c = 4 : 5, then a : c equals:
A2 : 5
B3 : 4
C8 : 15
D5 : 8
Answer & Solution
Correct answer: C. 8 : 15
1. The two ratios cannot be chained until b means the same amount in both.
2. In the first b is 3 and in the second b is 4, so scale each to their LCM, 12.
3. Multiply the first by 4: a : b = 8 : 12.
4. Multiply the second by 3: b : c = 12 : 15.
5. Now a : b : c = 8 : 12 : 15, so a : c = 8 : 15. Answering 2 : 5 comes from multiplying the outer terms without matching b.
_Source: NCERT Class 8 Maths, Ch 7 'Comparing Quantities', S7.1 Recalling Ratios and Percentages_
Related questions
Those two workers, at that combined rate, finish the whole job in:A worker finishing in 5 hours and another in 20 hours together do what share of the job eaConverting two fifths of an hour into minutes gives:In work problems, the parts of the job done by each worker in one hour add up to:Flying into that same 30 mph wind, the same plane's ground speed would be:A plane's ground speed with a tailwind of 30 mph, if the plane itself flies at 150 mph, isOn that drive, Tony's interstate speed was:Tony drives 4 hours in all, 208 miles on the interstate and 40 on country roads, going 15