Answer:
133·34%
Step-by-step explanation:
Let the third number be x
40% of the third number is (40 ÷ 100) × x = 0·4 × x
As the first number is 40% less than the third number, it means that the first number is x - 0·4 × x = 0·6 × x
20% of the third number is (20 ÷ 100) × x = 0·2 × x
As the second number is 20% less than the third number, it means that the second number is x - 0·2 × x = 0·8 × x
Let the percentage of the first number that forms the second be k%
∴ (k ÷ 100) × 0·6 × x = 0·8 × x
⇒ (k ÷ 100) = 4 ÷ 3
∴ k ≈ 133·34
∴ The percentage of the first number that forms the second is 133·34%