Which mode of travel is used by the most number of students? Which mode of travel is used by the least number of students?
Answer
First read the key printed beside the pictograph: one symbol = 1 student. So nothing has to be multiplied here — just count the symbols in each row.
The pictograph of page 79, read row by row. The school bus row is the longest and the cycle row the shortest.
Modes of Travelling
Symbols counted
Number of Students
Private car
4
4
Public bus
5
5
School bus
11
11
Cycle
3
3
Walking
7
7
Total
30
30
School bus 11 > Walking 7 > Public bus 5 > Private car 4 > Cycle 3
The school bus is used by the most number of students (11), and the cycle by the least number of students (3).
Total students surveyed = 4 + 5 + 11 + 3 + 7 = 30
Why a pictograph answers so fast: your eye compares lengths of rows far more quickly than it compares numbers written in a table. The longest and the shortest row are spotted before you count anything at all.
Q2.
What is the number of children who always slept at least 9 hours at night?
Answer
The key says one symbol stands for 10 children. The row ‘Always’ has 5 complete symbols.
5 symbols × 10 children each = 50 children
Nand Kishor's pictograph. One circle = 10 children; a half circle = 5 children.
Answer: 50 children.
Tip: never read a pictograph without reading its key first. The very same picture would mean 5 children if the key said “= 1 child”, and 500 if it said “= 100 children”.
Q3.
How many children sometimes slept at least 9 hours at night?
Answer
The row ‘Sometimes’ has 2 complete symbols and 1 half symbol.
2 complete symbols = 2 × 10 = 20 children
1 half symbol = half of 10 = 5 children
Total = 20 + 5 = 25 children
Answer: 25 children.
Why a half symbol is allowed: the scale here is 10, so numbers like 25 are not exact multiples of the scale. Drawing half a picture is the pictograph's way of showing “half of 10”, that is 5. Values such as 23 or 27 could still not be shown neatly — that is a real limitation of pictographs.
Q4.
How many children always slept less than 9 hours each night? Explain how you got your answer.
Answer
“Always slept less than 9 hours” is the same as “never slept at least 9 hours”. So we read the row ‘Never’.
Never → 4 complete symbols
4 × 10 = 40 children
Answer: 40 children.
How the answer was found: the trick is in the words, not in the arithmetic. A child who never sleeps 9 hours or more must be sleeping less than 9 hours on every night — that is, always less than 9 hours. So the two sentences describe exactly the same group of children.
Check it yourself: 50 + 25 + 40 = 115 children answered Nand Kishor's survey in all.