two containers of equal capacity are full of a mixture of oil and water. In the first, the ratio of oil to water is 4 : 7 and in the second it is 7 : 11. Now both the mixtures are mixed together in a container. What is the resulting ratio of oil to water?

Container 1: ratio 4:7 means oil = 4/(4+7) = 4/11, water = 7/11. Container 2: ratio 7:11 means oil = 7/18, water = 11/18. Taking equal capacity (LCM = 198), Container 1: oil = 4/11 × 198 = 72, water = 126. Container 2: oil = 7/18 × 198 = 77, water = 121. Combined: oil = 72+77 = 149, water = 126+121 = 247. Ratio = 149:247.