MERCER — A 20-year-old Grove City man convicted of having sex with a girl and robbing a man at knife point could be pushing 40 by the time he gets out of prison.

Nicholas A. Robinson last week was sentenced in Mercer County Court to a combined 7 to 20 years in state prison in the separate first-degree felony cases.

Robinson on July 11 pleaded guilty in both cases.

The defendant has been in the Mercer County Prison since Feb. 22, a day after Grove City police arrested him in a strong-arm robbery at a home in the 500 block of North Center Street.

Police said Robinson showed up at the apartment demanding money from a man who was visiting there. He brandished a knife and stole $83 from the victim, who he previously knew.

He eventually pleaded guilty to a top count of robbery.

A week following his arrest, Grove City police charged him with having a sexual relationship with a 14-year-old girl between March and December 2015.

He eventually pleaded in that case to a top count of involuntary deviate sexual intercourse with a person less than 16 years old.

Mercer County Judge Robert Yeatts on Oct. 25 sentenced Robinson to 5 to 15 years in prison in the sex case and 2 to 5 years in the robbery case.

Yeatts ordered the sentences to run consecutively, meaning the defendant will serve 7 to 20 years.

Additionally, Robinson was deemed a Tier 3 offender under the state’s version of Megan’s Law.

The designation means that upon being paroled or completing his sentence, he must regularly register his whereabouts to police for the rest of his life.