Correct Answer: 40 and 16

Solution : Given:
4 + 40 × 5 – 16 ÷ 8 = 79

Let's check the options –
First option: 16 and 4
On interchanging the numbers, we get –
16 + 40 × 5 – 4 ÷ 8 = 79
Solving the L.H.S. of the given equation –
= 16 + 40 × 5 – 4 ÷ 8
= 16 + 40 × 5 – 0.5
= 16 + 200 – 0.5
= 215.5 ≠ 79
Second option: 4 and 40
On interchanging the numbers, we get –
40 + 4 × 5 – 16 ÷ 8 = 79
Solving the L.H.S. of the given equation –
= 40 + 4 × 5 – 16 ÷ 8
= 40 + 4 × 5 – 2
= 40 + 20 – 2
= 58 ≠ 79
Third option: 5 and 16
On interchanging the numbers, we get –
4 + 40 × 16 – 5 ÷ 8 = 79
Solving the L.H.S. of the given equation –
= 4 + 40 × 16 – 5 ÷ 8
= 4 + 40 × 16 – 0.625
= 4 + 640 – 0.625
= 643.375 ≠ 79
Fourth option: 40 and 16
On interchanging the numbers, we get –
4 + 16 × 5 – 40 ÷ 8 = 79
Solving the L.H.S. of the given equation –
= 4 + 16 × 5 – 40 ÷ 8
= 4 + 16 × 5 – 5
= 4 + 80 – 5
= 79 = R.H.S.

So, only the fourth option satisfies the R.H.S. of the equation. Hence, the fourth option is correct.