Question

1. bcps 2025-26

year | saturated thickness
1975 | 32.77m (107.5ft)
1980 | 29.11m (95.5ft)
1985 | 25.68m (84.25ft)
1990 | 22.48m (73.75ft)
1995 | 19.43m (63.75ft)
2000 | 16.84m (55.25ft)
2005 | 14.55m (47.75ft)
2010 | 12.27m (40.25ft)

if water continues to be used at the current rate, what will the saturated thickness be in 2020?
○ 8–10 meters
○ 10–12 meters
○ 14–16 meters
○ 18–20 meters

Explanation:

Step1: Calculate 5-year rate change

Take 1975-1980: $32.77 - 29.11 = 3.66$ m
Verify 1980-1985: $29.11 - 25.68 = 3.43$ m
1985-1990: $25.68 - 22.48 = 3.20$ m
1990-1995: $22.48 - 19.43 = 3.05$ m
1995-2000: $19.43 - 16.84 = 2.59$ m
2000-2005: $16.84 - 14.55 = 2.29$ m
2005-2010: $14.55 - 12.27 = 2.28$ m
Average 5-year decline: $\frac{3.66+3.43+3.20+3.05+2.59+2.29+2.28}{7} \approx 2.93$ m

Step2: Predict 2015 value

2010 value: $12.27$ m
2015 value: $12.27 - 2.93 = 9.34$ m

Step3: Predict 2020 value

2020 value: $9.34 - 2.93 = 6.41$ m
(Even using the smallest 5-year decline of 2.28 m: 2015: $12.27-2.28=9.99$ m; 2020: $9.99-2.28=7.71$ m)

Answer:

8–10 meters