The mass of a box measured by grocer's balance is 4.2 kg. Two additional masses 10.20 g and 15.25 g are added to the box. What is the total mass of the box?

Explanation

To find the total mass of the box after adding two additional masses, we can follow these steps:

### Step 1: Identify the mass of the box
The mass of the box is given as 4.2 kg.

### Step 2: Convert the additional masses from grams to kilograms
We have two additional masses:
- The first mass is 10.20 g. To convert this to kilograms:
\[ 10.20 \, \text{g} = \frac{10.20}{1000} = 0.01020 \, \text{kg} \]

- The second mass is 15.25 g. To convert this to kilograms:
\[ 15.25 \, \text{g} = \frac{15.25}{1000} = 0.01525 \, \text{kg} \]

### Step 3: Calculate the total mass
Now, we can find the total mass by adding the mass of the box and the two additional masses:
\[ \text{Total mass} = \text{mass of box} + \text{mass 1} + \text{mass 2} \]
Substituting the values we have:
\[ \text{Total mass} = 4.2 \, \text{kg} + 0.01020 \, \text{kg} + 0.01525 \, \text{kg} \]

### Step 4: Perform the addition
Calculating the total:
\[ \text{Total mass} = 4.2 + 0.01020 + 0.01525 = 4.22545 \, \text{kg} \]

### Step 5: Round to the appropriate number of significant figures
Since the mass of the box (4.2 kg) is given to one decimal place, we should round the total mass to one decimal place as well:
\[ \text{Total mass rounded} = 4.2 \, \text{kg} \]

### Final Answer:
The total mass of the box is **4.2 kg**.

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