Question 705008

SCQMEDIUM

Among 1000 squirrel babies, 200 have three stripes on their back, 500 have two stripes on their back and the rest have four stripes on their back. While 90% of the three-striped babies survive to adulthood, only 80% of the two-striped and 70% of the four-striped babies survive to adulthood. The fraction of four-striped squirrels among the adults is nearest to

(A)

0.21

(B)

0.3

(C)

0.266

(D)

0.228

Detailed Solution

3-striped adults = 200×0.9=180200 \times 0.9 = 180. 2-striped adults = 500×0.8=400500 \times 0.8 = 400. 4-striped babies = 1000−200−500=3001000 - 200 - 500 = 300. 4-striped adults = 300×0.7=210300 \times 0.7 = 210. Total adults = 180+400+210=790180 + 400 + 210 = 790. Fraction of 4-striped = 210790≈0.2658≈0.266\frac{210}{790} \approx 0.2658 \approx 0.266.

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