WASHINGTON — Mortgage rates sank this week, with rates on 30-year mortgages dropping to a six-month low, a spot of welcome news to would-be home buyers.

Freddie Mac, the mortgage company, reported Wednesday, that 30-year, fixed-rate mortgages averaged 6.20 percent. That was down from 6.24 percent last week and was the lowest rate since the week ending May 10, when rates stood at 6.15 percent.

Other mortgage rates also fell.

Rates on 15-year fixed-rate mortgages, a popular choice for refinancing, slid to 5.83 percent, from 5.88 percent last week. This week's rate hasn't been lower since the week ending Feb. 2, 2006, when 15-year rates averaged 5.81 percent, the mortgage company said.

For five-year adjustable-rate mortgages, rates fell to 5.88 percent, down from 5.96 percent last week. This week's rate hasn't been lower since the week ending May 3, when 5-year rates averaged 5.87 percent, Freddie Mac said.

Rates on one-year adjustable-rate mortgages dropped to 5.42 percent, compared with 5.50 percent last week. The rate on one-year ARMs hasn't been lower since late March, when rates averaged 5.40 percent.

The moderation in mortgage rates around the country provides a dose of good news for prospective home buyers, some of whom also may be facing a situation of harder-to-get credit.

But the easing in mortgage rates doesn't change housing's overall bleak picture.