Make the common term Adults the same number of units in both ratios to form a three-way ratio.<br><br>
• Adults : Boys = 10 : 1<br>
• Adults : Girls = 5 : 2 = 10 : 4<br>
• So Adults : Boys : Girls = 10 : 1 : 4<br>
• 10 units of adults = 250, so 1 unit = 250 ÷ 10 = 25<br>
• Boys = 1 × 25 = 25<br>
• Girls = 4 × 25 = 100<br>
• Total = 250 + 25 + 100 = 375<br><br>
Final Answer: 375