00273    a2200097   4500020001500000082001800015245005900033260004000092300001500132650002800147  a0335142702  a004.0151bOPE  aChapter 1 numbers and machinesbBlock I (Chapters 1-3)  aWaltonbOpen Universityc1988g1988  a51p.c29cm  aMathematical principles