created 08/02/99

# Chapter 12 Programming Exercises

## Exercise 1 --- Discount Prices

During a special sale at a store, a 10% discount is taken on purchases over \$10.00. Write a program that asks for the amount of purchases, then calculates the discounted price. The purchase amount will be input in cents (as an integer):

```Enter amount of purchases:
2000
Discounted price: 1800
```

Use integer arithmetic throughout the program.

## Exercise 2 --- Order Checker

Bob's Discount Bolts charges the following prices:

• 5 cents per bolt
• 3 cents per nut
• 1 cent per washer

Write a program that asks the user for the number of bolts, nuts, and washers in their purchase and then calculates and prints out the total. As an added feature, the program checks the order. It is usually a mistake if there are more bolts than nuts. In this case the program writes out "Check the Order." Otherwise the program writes out "Order is OK." In either case the total price is written out.

```Number of bolts:
12
Number of nuts:
8
Number of washers:
24

Check the Order

Total cost: 108
```

Use constants for the unit cost of each item. In other words, declare something like `final int boltPrice = 5;` and so on in your program.

## Exercise 3 --- Last Chance Gas

Al's Last Chance Gas station sits on Route 190 on the edge of Death Valley. There is no other gas station for 200 miles. You are to write a program to help drivers decide if they need gas. The program asks for:

• The capacity of the gas tank, in gallons.
• The indication of the gas gauge in percent (full= 100, three quarters full = 75, and so on).
• The miles per gallon of the car.

The program then writes out "Get Gas" or "Safe to Proceed" depending on if the car can cross the 200 miles with the gas remaining in the tank.

```Tank capacity:
12
50
Miles per gallon:
30
Get Gas!
```

Use integers for all input and all arithmetic.

## Exercise 4 --- Pie Eating Contest

At the State Fair Pie Eating Contest all contestants in the heavyweight division must weigh within 30 pounds of 250 pounds. Write a program that asks for a contestant's weight and then says if the contestant is allowed in the contest.

## Exercise 5 --- Ground Beef Value Calculator

Different packages of ground beef have different percentages of fat and different costs per pound. Write a program that asks the user for:

1. The price per pound of package "A"
2. The percent lean in package "A"
3. The price per pound of package "B"
4. The percent lean in package "B"

The program then calculates the cost per pound of lean (non-fat) beef for each package and writes out which is the best value.

```Price per pound package A:
2.89
Percent lean package A:
85
Price per pound package B:
3.49
Percent lean package B:
93

Package A cost per pound of lean:3.4
Package B cost per pound of lean:3.752688
Package A is the best value
```

Assume that the two packages will not come out equal in value.

## Exercise 5 --- Y2K Problem Detector

Write a program that asks a user for their birth year encoded as two digits (like "62") and for the current year, also encoded as two digits (like "99"). The program is to correctly write out the users age in years.

```Year of Birth:
62
Current year:
99

----- another run of the program --------
Year of Birth:
62
Current year:
00

```

## Exercise 6 --- Wind Chill Index

(You will need to include java.Math.* and use floating point input for this exercise.)

The wind chill index (WCI) is calculated from the wind speed `v` in miles per hour and the temperature `t` in Fahrenheit. Three formulas are used, depending on the wind speed:

```if (0 <= v <= 4) then WCI = t

if (v >=45) then WCI = 1.6t - 55

otherwise, WCI = 91.4 + (91.4 - t)(0.0203v - 0.304(v)1/2 - 0.474)
```

To calculate `(v)1/2` use `Math.sqrt( double )`.