Question

the graph below shows the amounts of rainfall for six months.
rainfall amount (in mm)
70
60
50
40
30
20
june july august september october november
month
(a) what was the greatest amount of rainfall in a month?
mm
(b) when did the amount have the greatest decrease?
june to july
july to august
august to september
september to october

Explanation:

Part (a)

Step1: Analyze the graph's y - axis

The y - axis of the graph represents the rainfall amount in mm. We need to find the highest point on the graph.

Step2: Identify the highest data point

Looking at the graph, the data point for November is the highest. By checking the y - axis scale, we can see that the value corresponding to November's rainfall is 65 mm (or we can see from the graph that the topmost point is at 65 mm, since the intervals are 10 mm, and the point is between 60 and 70, closer to 65? Wait, actually, looking at the graph: June is around 55, July around 35, August around 50, September around 45, October around 60, November around 65. Wait, maybe the y - axis has marks at 20,30,40,50,60,70. So the points: June is at 55 (between 50 and 60), July at 35 (between 30 and 40), August at 50, September at 45 (between 40 and 50), October at 60, November at 65 (between 60 and 70). So the greatest amount is 65 mm? Wait, maybe I misread. Wait the graph: the y - axis is labeled with 20,30,40,50,60,70. The points: June: the dot is at 55 (midway between 50 and 60), July: midway between 30 and 40 (35), August: at 50, September: midway between 40 and 50 (45), October: at 60, November: midway between 60 and 70 (65). So the highest is November's 65 mm. Wait, maybe the exact value: let's see the vertical lines. The distance between 50 and 60 is 10, so each small division? Wait maybe the graph has the November point at 65. Alternatively, maybe the y - axis is such that the top mark is 70, and the November point is at 65. So the greatest amount of rainfall in a month is 65 mm.

Step1: Calculate the decrease for each interval

• June to July: Rainfall in June (let's say \( R_J = 55 \) mm) and July (\( R_{Ju}=35 \) mm). Decrease \( = 55 - 35=20 \) mm.
• July to August: \( R_{Ju}=35 \) mm, \( R_A = 50 \) mm. This is an increase, not a decrease.
• August to September: \( R_A = 50 \) mm, \( R_S = 45 \) mm. Decrease \( = 50 - 45 = 5 \) mm.
• September to October: \( R_S = 45 \) mm, \( R_O = 60 \) mm. This is an increase, not a decrease.

Step2: Identify the greatest decrease

Among the decreases (June - July: 20 mm, August - September: 5 mm), the greatest decrease is from June to July.

Answer:

(a): 65

Part (b)