Wearing baggy pants and cornrows, a group of hip-hop musicians peddles CDs at the corner of 18th and K streets NW. Lyrics blast out of speakers, the 10-inch woofers and two-inch tweeters that sit in the back of their van. Listen:

"Seven times 5 equals 35! (Don' stop!) Seven times 6 equals 42! (Wha?)"

Okay, so these aren't Eminem lyrics -- and that's the point. David Printis Sr., his son D.J. and his nephews Alonzo Powell and Everett Roundtree are selling not bootleg rap CDs but "Multiplication Hip-Hop." It's intended to teach math to a generation already fluent in rhymes.

Tina Wynn, a single mother from Silver Spring, bought "Multiplication Hip-Hop" for her son Deonte, 9. "Every day he plays it," Wynn says, rolling her eyes. "All day, every day. It just wears me out."

But guess what? Deonte knows his times tables. He knows them so well that Wynn recommended the CDs to her son's teacher, who uses them in her classroom.

Diane Fingers, principal at Indian Queen Elementary School in Fort Washington, says her students listen to the CDs even when they don't have to, at home and during recess.

"They like the beat; they pick up on the rhythm," Fingers says. "Then they pick up on the facts."

Karen Kunkel, principal at Green Valley Elementary in Temple Hills, began using "Multiplication Hip-Hop" last year to teach her second-graders, and believes the CD is at least partly responsible for her school's improvement on the Comprehensive Test of Basic Skills, a standardized test given to second-graders in Maryland. In the 2001-2002 school year, 23 percent of her second-graders were proficient in math. This past school year, that number was 72 percent. Educators have long used music to dispel the boredom of rote memorization. If you grew up in the 1970s or '80s, you had "Schoolhouse Rock." These kids have Schoolhouse Rap.

Martin L. Johnson, professor of mathematics education at the University of Maryland at College Park, says: "Kids learn the alphabet by learning a song; they learn to count by putting it in a song. This is just another way of bringing it to life for kids."

Printis's line of CDs (available at De-URecords.com) is one of many that use hip-hop to teach children about the world. Chuck Herring, a Pittsburgh educator, regularly transforms himself from a mild-mannered college professor into Grammar Man, a superhero who travels to elementary schools to battle his evil arch-enemy, Double Negative, using nothing but beats, rhymes and a comprehensive knowledge of the English language.

"I saw how my kids knew all the words to Tupac, Wu-Tang, Biggie," says Herring, who wears red tights and a bright yellow cape when he's the super-grammarian. "But they didn't know what an adjective was! So I came up with a little ditty about adjectives." Herring's company blossomed from there, producing "Black History Is Not Just a Month," a CD about black heroes such as Nat Love, Muhammad Ali and Bill Cosby. He now has "The Mathematics Magician" and "The Amazing Adventures of Grammar Man," all of which are available at hiphopkids.com. Herring recently began shooting a live-action children's show starring Grammar Man, which he hopes will get picked up as a TV series.

In New York, Shawn C. Chandler and his partner Ronald C. Speed-Bey Jr. have come up with their versions of the learning tools, available at sing2school.com. In his classroom in Queens, Chandler used to teach math with a program called "Rock and Learn," a cheesy rock album from Texas. To the kids at IS 231, it went down like Brussels sprouts.

"Times are changing, kids are changing, and we need to offer music that the kids relate to," Chandler says. "Now you have this merger of hip-hop and education."

Chandler's brand of hip-hop was realistic enough to hook 12-year-old Emmanuel George of Queens. Emmanuel never used to like math. Now, says his mother, Elena, "he listens to that CD so much I have to tell him to turn it off."

Elena used to work at a hair salon, and she would mention the CDs to every customer she could. "Anybody who had a kid who was having any kind of math problems, [I'd tell them] 'Get these CDs. He'll know the multiplication tables faster than you can think.' "

The idea for "Multiplication Hip-Hop" came to Printis in 1999, when he was recording demos in a small studio in his home in Fort Washington. Printis's son D.J. supplied most of the vocals, simplifying his speech patterns and digitally changing his voice from a growling rapper into a Woody Woodpecker. By October 2000, the CDs were ready, and Printis and his crew brought "Multiplication Hip-Hop" to the Million Family March. Wearing sandwich boards and passing out fliers, they sold 60 copies. Printis and his boys sell CDs every day, either downtown or in Mitchellville or Bowie. Sometimes they'll sell 120 on a lunch hour.

"I never really thought it was gonna go so big," Printis says.

This lunch hour, Tina Wynn can't help but nod along with "Multiplication Hip-Hop."

Standing next to her, listening to the music: "Nine times 12 equals 108 (That's right!)." And you're thinking: Is that right?

"Some adults don't even know their times tables," says Wynn. "I listen to it, too, just to brush up."

D.J., left, and David Printis take stock of their inventory of CDs. At left: Everett Roundtree and David Printis Sr. chat with customers Rosa Speight and Georgette Fogle, from left, at their sound-equipped van downtown; right, Pam Martin questions Printis and Robert Kelly, right, about a CD.