Explanation:
this means nothing else than that these
3.3 × 10⁵ J (in 200 seconds)
are 91% of the total energy.
in other words,
the efficiency of the kettle to apply the provided energy to the contained water is
(3.3 × 10⁵) / (total energy) = 91/100
remember, x% always means x/100 of the total amount.
from
(3.3 × 10⁵) / (total energy) = 91/100
we get
100×(3.3 × 10⁵) / (total energy) = 91
100×(3.3 × 10⁵) = 91 × (total energy)
total energy = 100×(3.3 × 10⁵)/91 = 330×10⁵/91 =
= 33,000,000 / 91 =
= 362637.362637362637362637... ≈
≈ 3.6 × 10⁵ J in 200 s