Which two numbers (not digits) and two signs need to be interchanged to make the given equation correct?
$$28 \times 4 + 15 \div 8 - 34 = 388$$

Solution

Option (a) $$\times$$ and $$\div$$; 28 and 8

$$8 \div 4 + 15 \times 28 - 34 = 388$$

$$2 + 420 - 34 = 388$$

388 = 388

The given equation is satisfied. So this is the correct answer.

Option (b) $$+$$ and $$\div$$; 4 and 34

$$28 \times 34 \div 15 + 8 - 4 = 388$$

$$28\times\frac{34}{15}+8-4\ne\ 388$$

The given equation is not satisfied. Because it will give values in fractions. So this is not the correct answer.

Option (c) $$-$$ and $$\times$$; 15 and 28

$$15 - 4 + 28 \div 8 \times 34 = 388$$

$$15-4+\frac{28}{8}\times34=388$$

$$15-4+7\times17=388$$
$$11+119=388$$
$$130\ne388$$
The given equation is not satisfied. So this is not the correct answer.
Option (d) $$+$$ and $$\times$$; 15 and 8

$$28 + 4 \times 8 \div 15 - 34 = 388$$

The given equation is not satisfied. Because it will give values in fractions. So this is not the correct answer.