【文档说明】清华版英语三年级上册《unit 3 let's do math lesson 17》PPT课件(共15页).ppt，共(15)页，2.521 MB，由小喜鸽上传

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UNIT3LET’SDOMATHLESSON1720~90的十位数的整数均以后缀-ty结尾20twenty30thirty40forty50fifty60sixty70seventy80eighty90ninetyAga

in2030405060twentythirtyfortyfiftysixty708090100seventyeightyninetyonehundredLet’sdoitTherearefortybananas.Mybrothertookawayten.H

owmanybananasareleft?40-10=30Fortyminustenisthirty.Thirtybananasareleft.Therearefiftyapples.Mysistertookawaytwenty.Howmanyapplesareleft?50-20=30Fift

yminustwentyisthirty.Thirtyapplesareleft.Therearefiftyeggs.Mymothertookawaythirty.Howmanyeggsareleft?

50-30=20Fiftyminusthirtyistwenty.Twentyeggsareleft.Therearesixtypears.Myfathertookawayten.Howmanypearsareleft?60-10=50Sixtyminustenisfifty

.Fiftypearsareleft.Practice1.90-20=?2.80-20=?Ninetyminustwentyis________.Eightyminustwentyis________.Onehundredminustwe

ntyis________.3.100-20=?seventysixtyeightyFiftyminusthirtyis________.Sixtyminusthirtyis________.Ninetym

inusfortyis________.4.50-30=?5.60-30=?6.90-40=?twentythirtyfiftyHomework:回家把今天学到的数字数给爸爸妈妈听。