A ratio of $1:4$ means the first part is $\frac{1}{1+4}$ of the total.

Once you know how many fragile boxes are on each truck, subtract from 310 and 490 to get nonfragile boxes, then compare.

Define the totals: TA=310, TB=490, and T=TA+TB.

Let k be a slider, and define fragile counts as fA=3k, fB=5k, so f=fA+fB.

Nonfragile total is n=T-f.

Because fragile:nonfragile is $1:4$, graph:

• y1 = f/(T-f)
• y2 = 1/4

Look for the intersection; its $k$-value makes the ratio correct.

Using the intersection’s $k$-value, compute nA=TA-fA and nB=TB-fB.

Then compute nB-nA (or put these expressions in a small table) to get the requested difference. Propеrt⁠у ​οf A‍nікο.аі

Let the number of fragile boxes on Truck A be $3k$ and on Truck B be $5k$.

Then the total number of fragile boxes is $3k+5k=8k$.

The total number of boxes is $310+490=800$.

The ratio fragile:nonfragile is $1:4$, so fragile boxes are $\frac{1}{1+4}=\frac{1}{5}$ of all boxes.

So the total number of fragile boxes is:

Thus $8k=160$.

From $8k=160$, we get $k=20$.

Fragile boxes:

• Truck A: $3k=3(20)=60$

• Truck B: $5k=5(20)=100$

Nonfragile boxes:

• Truck A: $310-60=250$

• Truck B: $490-100=390$

Truck B has $390-250=140$ more nonfragile boxes than Truck A. ©​ аnіко.​аі

Therefore, the correct choice is 140.