In the original condition, there are 4 variables (h:husband, w:wife x: son, y: son) and 1 equation (h+w+x+y=15,000). In order to match the number of variables and the number of equations, we need 3 equations. Since there are one condition 1) and one condition 2), we lack 2 equations. Therefore, there is high chance that E is likely the answer.
However, the condition 1) has 2 equations and the condition 2) has 3 equations. So, the condition 2) is sufficient and the correct answer is B.
- For cases where we need 3 more equations, such as original conditions with “3 variables”, or “4 variables and 1 equation”, or “5 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 80% chance that E is the answer (especially about 90% of 2 by 2 questions where there are more than 3 variables), while C has 15% chance. These two are the majority. In case of common mistake type 3,4, the answer may be from A, B or D but there is only 5% chance. Since E is most likely to be the answer using 1) and 2) separately according to DS definition (It saves us time). Obviously there may be cases where the answer is A, B, C or D.