放学后小华和小夏从学校分别沿东南方向和西南方向回家，若小华和小夏走的速度都是40米/分，小华15分钟到家，小夏20分钟到家，小华和小夏家的直线距离是（     ）米．

Most of the world’s victims of AIDS live—and, at an alarming rate, die—in Africa. The number of people living with AIDS in Africa was estimated at 26.6 million in late 2003. New figures to be published by the United Nations Joint Program on AIDS (UNAIDS), the special UN agency set up to deal with the pandemic, will probably confirm its continued spread in Africa, but they will also show whether the rate of spread is constant, increasing or falling. AIDS is most prevalent in Eastern and Southern Africa, with South Africa, Zimbabwe and Kenya having the greatest numbers of sufferers; other countries severely affected include Botswana and Zambia. AIDS was raging in Eastern Africa—where it was called "slim", after the appearance of victims wasting away—within a few years after its emergence was established in the world in 1981. One theory of the origin of the virus and syndrome suggests that they started in the eastern Congo basin; however, the conflicting theories about the origin of AIDS are highly controversial and politicized, and the controversy is far from being settled. Measures being taken all over Africa include, first of all, campaigns of public awareness and device, including advice to remain faithful to one sexual partner and to use condoms. The latter advice is widely ignored or resisted owing to natural and cultural aversion to condoms and to Christian and Muslim teaching, which places emphasis instead on self-restraint. An important part of anti-AIDS campaigns, whether organized by governments, nongovernmental organizations or both, is the extension of voluntary counseling and testing (VCT). In addition, medical research has found a way to help sufferers, though not to cure them.Funds for anti-AIDS efforts are provided by the Global Fund to Fight AIDS, Tuberculosis and Malaria, a partnership between governments, civil society, the private sector and affected communities around the world; the fund was launched following a call by the UN Secretary-General in 2001. However, much more is needed if the spread of the pandemic is to be at least halted.