Explanation for Question 20 From the Math (Calc) Section on the 2018 March Sat
Question 20 says on average, 2 10% of the net energy of one Tropic level is transferred to the next 3 topic level in an ecosystem, based on the energy pyramid of primary 4 producers have 5,000 joules of energy, 5 approximately how much of this energy in calories, 6 it's transferred to the secondary consumers in this ecosystem. 7 So we know that primary producers have 5,000 joules of energy 8 and that to get to the secondary producers, 9 we're going to multiply this by 0.1 twice 10 because only 10% of the energy is transferred to the next Tropic level. 11 So that means we can multiply 5,000 by 0.1 12 times 0.1, which is just your 0.01. 13 And that gives us 50. So we know that secondary consumers get 50 14 joules of energy, but now we need to, 15 uh, translate that into calories. 16 And we know that one calorie is equal to four point 18 17 jewels. So we're going to multiply 50 by one, 18 over four point 18. The Juul is cancel out and this gives us 19 11.96, 20 which is answer choice a.