Earthwork Arithmetic: Average End Areas and Unequal Intervals

Earthwork Arithmetic: Average End Areas and Unequal Intervals

Original quantitative learning practice in English. All 24 questions are included. Four supplied cases exercise six related calculation targets; they form one topic, not four separate tests. Every question includes the complete initial data. Use the stated model and retain intermediate precision. Choose one answer. Learning target: 20/24, not an official pass mark. This bank covers the calculation topic in its title; it is not a complete professional examination, design approval or operating instruction.
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Three successive cut cross-sections have areas 8, 14, 10 m². The first interval is 15 m and the second is 25 m. Assume area varies linearly along each interval, so interval volume is length times the mean of its two endpoint areas. All sections are cut; no density changes or earth-moving factors apply. Calculate the mean area for the first interval in m². Keep intermediate values unrounded; round the final result to four decimal places if necessary.