To find the total grams of cereal in the whole box, we can set up the equation using the given information. We know that 60% of the whole box is equal to 420 grams.
We can set up the equation as follows:
\[ \frac{part}{whole} = \frac{60}{100} = \frac{420}{x} \]
Where \( x \) is the total grams in the box.
Cross-multiplying gives us:
\[ 60x = 420 \times 100 \]
Calculating \( 420 \times 100 \):
\[ 420 \times 100 = 42000 \]
So we have:
\[ 60x = 42000 \]
Now, to isolate \( x \), we divide both sides by 60:
\[ x = \frac{42000}{60} \]
Calculating \( \frac{42000}{60} \):
\[ 42000 รท 60 = 700 \]
Thus, there are 700 grams in the whole box.
In summary:
700 g in the box.