6th Class Mathematics Knowing our Numbers

  • question_answer 18)                 Give a rough estimate (by rounding off to nearest hundreds) and also a closer estimate (by rounding off to nearest tens). (a) 439 + 334 + 4317                                                         (b) 1,08,734 ? 47,599 (c) 8325 ? 491                                                                     (d) 4,89,348 ? 48,365

    Answer:

                    (a) We have, 439 + 334 + 4317 \[\because \] \[\left. \begin{align}   & 439\to 400 \\  & 334\to 300 \\  & 4317\to 4300 \\ \end{align} \right\}\]      [rounding off to nearest hundreds] \[\therefore \] Rough estimate = 439 + 334 + 4317 = 400 + 300 + 4300 = 5000 Again, \[\left. \begin{align}   & 439\to 440 \\  & 334\to 330 \\  & 4317\to 4320 \\ \end{align} \right\}\] [rounding off to nearest tens and closer estimate = 439 + 334 + 4317 = 440 + 330 + 4320 = 5090 (b) We have, 1,08,734 ? 47599 \[\because \] \[\left. \begin{align}   & 1,08,734\to 1,08,700 \\  & 47,599\to 47,600 \\ \end{align} \right\}\]      [rounding off to nearest hundreds] \[\therefore \] Rough estimate = 1,08,734 ? 47,599 = 1,08,700 ? 47,600 = 61,100 Again, \[\left. \begin{align}   & 1,08,734\to 1,08,730 \\  & 47,599\to 47,600 \\ \end{align} \right\}\]      [rounding off to nearest tens] and closer estimate = 1,08,734 ? 47,599 = 1,08,730 ? 47,600 = 61,130 (c) We have, 8325 ? 491 \[\because \] \[\left. \begin{align}   & 8325\to 8300 \\  & 491\to 500 \\ \end{align} \right\}\]                      [rounding off to nearest hundreds] \[\therefore \] Rough estimate = 8325 ? 491 = 8300 ? 500 = 7800 Again, \[\left. \begin{align}   & 8325\to 8330 \\  & 491\to 490 \\ \end{align} \right\}\]                      [rounding off to nearest tens] and closer estimate = 8325 ? 491 = 8330 ? 490 = 7840 (d) We have, 4,89,348 ? 48,365 \[\because \] \[\left. \begin{align}   & 489348\to 4,89,300 \\  & 48,365\to 48,400 \\ \end{align} \right\}\]      [rounding off to nearest hundreds] \[\therefore \] Rough estimate = 439,348 ? 48,365 = 4,89300 ? 48,400 = 4,40,900 Again, \[\left. \begin{align}   & 4,89,348\to 4,89,350 \\  & 48,365\to 48,370 \\ \end{align} \right\}\]      [rounding off to nearest tens] and closer estimate = 439,348 ? 48365 = 439350 ? 48,370 = 4,40,980


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