The Bengals were home for their Week 10 match-up with the San Diego Chargers.  The Bengals struck first, with fullback Jeremi Johnson's 3-yard TD run.  Running back Rudi Johnson scored next on 7-yard TD run. Quarterback Carson Palmer completed a 51-yard pass to wide receiver Chad Johnson for the third touchdown of the first quarter.  In the second quarter, the Chargers managed to get on the board with running back LaDainian Tomlinson's 9-yard touchdown run.  Cincinnati responded with 7-yard touchdown reception by wide receiver Chris Henry. In the third quarter, Tomlinson scored again on a 4-yard touchdown run, and quarterback Philip Rivers threw a 46-yard touchdown pass to Charger wide receiver Malcom Floyd. The Bengals responded with kicker Shayne Graham's 21-yard field goal.  The Chargers struck again on Rivers's 9-yard touchdown pass to tight end Brandon Manumaleuna. Bengals countered with Palmer throwing a 73-yard touchdown to Chad Johnson.  In the fourth quarter, San Diego took the lead, when Tomlinson scored on 2-yard and 9-yard touchdown runs. Graham kicked another field goal for the Bengals, from 44 yards out, but the Chargers held the lead, and Rivers tossed a final 5-yard touchdown pass to Manumaleuna. The Bengals' record fell to 4-5 with the loss.

Answer this question based on the article: How many of the touchdowns were passing touchdown?
6