| Out of 4 numbers, whose average is 60, the first one is one-fourth of the sum of the last three. The first number is [SSC (CGL) 2011] |
A) 15
B) 45
C) 48
D) 60
Correct Answer: C
Solution :
| Let the first number be x. |
| According to the question, |
| First number = (sum of all 4 numbers) |
| \[-\left( \frac{1}{4}\text{sum}\,\,\text{of}\,\,\text{last}\,\,\text{3}\,\,\text{numbers} \right)\] |
| \[\Rightarrow \]\[x=4\times 60-4x\] |
| \[\Rightarrow \]\[4x+x=240\]\[\Rightarrow \]\[5x=240\] |
| \[\Rightarrow \]\[x=\frac{240}{5}\]\[\Rightarrow \]\[x=48\] |
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