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A curve passing through the points as given in the table :

x123456789
y(x)0.20.711.31.51.71.92.12.3

the area bounded by the curve, the \(x\)-axis, \(x = 1\) and \(x = 9\) is :

  • A.11.5 sq. unit
  • B.12.0 sq. unit
  • C.10.5 sq. unit
  • D.10.2 sq. unit

Answer: A

The area is 11.5 sq. unit.

The table gives 9 equally spaced ordinates with \(h = 1\), that is 8 intervals, an even number, so Simpson's one-third rule applies:

\[ \begin{aligned} A &= \tfrac{h}{3}[(y_{1} + y_{9}) + 4(y_{2} + y_{4} + y_{6} + y_{8}) \\ &\quad + 2(y_{3} + y_{5} + y_{7})] \\ &= \tfrac{1}{3}[2.5 + 4(5.8) + 2(4.4)] \\ &= \tfrac{1}{3}(34.5) = 11.5 \end{aligned} \]

The trapezoidal rule gives \(1.25 + 10.2 = 11.45\), which also rounds to 11.5, so either standard rule leads to option A. 12.0, 10.5 and 10.2 are not produced by any rule; 10.2 is just the sum of the interior ordinates.

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