NCERT Solutions · Class 9 Mathematics How Quantities Combine: Understanding Data

(i) A student sleeps about $\displaystyle 8$ h, sits in class, at homework and meals for about $\displaystyle 9$ h, and is on her feet the rest. \[\text{Sahana: lying down } 8,\quad \text{sitting } 9,\quad \text{standing / moving } 7 \] \[8 + 9 + 7 = 24 \text{ h} \] Any other reasonable split adding to $\displaystyle 24$ h is also valid.(ii) \[\text{sitting } 10 \text{ h} > \text{lying down } 8 \text{ h} > \text{standing } 6 \text{ h} \] Most of Julie's waking day is spent sitting, so a desk job fits, for example a software engineer or an accountant. Guesses such as a driver or a tailor also fit; classmates' answers may differ.(iii) Each bar stands for $\displaystyle 24$ h, so a body-state takes \(\displaystyle \dfrac{\text{hours}}{24} \times 100\,\% \) of it. \[\frac{8}{24} \times 100 = 33.3, \qquad \frac{9}{24} \times 100 = 37.5, \qquad \frac{7}{24} \times 100 = 29.2 \] Share of the day in each body-state, in % (rounded to $\displaystyle 0.1$): \[\begin{array}{|l|c|c|c|} \hline & \text{Lying down} & \text{Sitting} & \text{Standing / moving} \\ \hline \text{Pavani} & 83.3 & 12.5 & 4.2 \\ \hline \text{Raghu} & 29.2 & 16.7 & 54.2 \\ \hline \text{Zakir} & 33.3 & 25.0 & 41.7 \\ \hline \text{Sahana} & 33.3 & 37.5 & 29.2 \\ \hline \text{Julie} & 33.3 & 41.7 & 25.0 \\ \hline \end{array} \]Answer: (i) Sahana: $\displaystyle 8$ h lying down, $\displaystyle 9$ h sitting, $\displaystyle 7$ h standing / moving (a guess). (ii) Julie probably has a desk job, as she sits for the longest. (iii) Sahana: $\displaystyle 33.3$% lying down, $\displaystyle 37.5$% sitting, $\displaystyle 29.2$% standing / moving; the other rows are in the table.