To find the probability of randomly selecting a type B plant, we first need to determine the total number of seedlings.
From the table, we have:
- Type A = 100
- Type B = 140
- Type C = 80
- Type D = 60
- Type E = 40
Now, we calculate the total number of seedlings:
\[ \text{Total seedlings} = 100 + 140 + 80 + 60 + 40 = 520 \]
Now that we have the total number of seedlings, we can calculate the probability of selecting a type B plant:
\[ \text{Probability of selecting type B} = \frac{\text{Number of type B seedlings}}{\text{Total number of seedlings}} = \frac{140}{520} \]
Next, we simplify the fraction \( \frac{140}{520} \):
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Find the greatest common divisor (GCD) of 140 and 520:
- The prime factorization of 140 is \( 2^2 \times 5 \times 7 \).
- The prime factorization of 520 is \( 2^3 \times 5 \times 13 \).
- The GCD is \( 2^2 \times 5 = 20 \).
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Divide both the numerator and denominator by their GCD:
\[ \frac{140 \div 20}{520 \div 20} = \frac{7}{26} \]
Thus, the probability that the farmer will randomly pick a type B plant is:
\[ \boxed{\frac{7}{26}} \]