Answer:
16.
Step-by-step explanation:
As per the question,
Number of words to be memorized = 20
Portion he has done = 4/5
No. Of words he has memorized so far = 20 * 4/5 = 16 words.
Thus, the no. of words that Ivan has memorized till now would be sixteen(16) as out of the total(five-fifths) which means five portions of four words each, Ivan has learned four of them that means 4*4 = 16. Therefore, 16(sixteen) is the answer.