A box is in the form of a cuboid whose external measures are 50cm x 40cm x 25cm.the base the side faces and back face are to be painted.find the area to be painted

2(40 \times 20) + (40 \times 25) = 2000 + 200 = 22002(40×20)+(40×25)= 2000+200= 2200

answer is 2200

Dimes= 20, Nickels= 15

Step-by-step explanation:

Since we are looking for the amount of coins, we can use system of equations to solve for the amount of coins.

Equation 1:

0.1x+0.05y=2.75

This equation comes from the total cost. x stands for dimes and y stands for nickels. 0.1 is the worth of a dime and 0.05 is the worth of a nickel.

Equation 2:

x=2y-10

This equation comes from 10 less than twice the number of nickels.

We can use substitution to find x and y.

0.1(2y-10)+0.05y=2.75

0.2y-1+0.05y=2.75

0.25y-1=2.75

0.25y=3.75

y=15

There are 15 nickels.

Now that we have y, we can plug it back into the equation to find x.

x=2(15)-10

x=30-10

x=20

There are 20 dimes.