Mental Strategies Check

{"questions":[{"content":"Calculate 59 + 24.<br>[[input-1]]","widgets":{"input-1":{"type":"input","answer":"83"}},"hints":["Add 1 to 59 to make 60."],"explanation":"60 + 23 = 83."},{"content":"Calculate 83 − 37.<br>[[input-2]]","widgets":{"input-2":{"type":"input","answer":"46"}},"hints":["Subtract 40, then add 3."],"explanation":"83 − 40 + 3 = 46."},{"content":"Calculate 198 + 35.<br>[[input-3]]","widgets":{"input-3":{"type":"input","answer":"233"}},"hints":["Treat 198 as 200 − 2."],"explanation":"200 + 35 − 2 = 233."},{"content":"Calculate 402 − 198.<br>[[input-4]]","widgets":{"input-4":{"type":"input","answer":"204"}},"hints":["Subtract 200, then add 2."],"explanation":"402 − 200 + 2 = 204."},{"content":"A notebook costs $27 and pens cost $16. What is the total cost?<br>[[input-5]]","widgets":{"input-5":{"type":"input","answer":"43"}},"hints":["Make 30 from 27."],"explanation":"27 + 16 = 30 + 13 = 43."},{"content":"Nora read 75 pages and had 28 pages left. How many pages had she read beyond the pages left?<br>[[input-6]]","widgets":{"input-6":{"type":"input","answer":"47"}},"hints":["Find 75 − 28."],"explanation":"75 − 30 + 2 = 47."},{"content":"Which compensation keeps 49 + 26 unchanged?<br>[[choice-7]]","widgets":{"choice-7":{"type":"choice","options":["50 + 25","50 + 26","48 + 25","49 + 25"],"answer":[0],"explanations":["50 + 25 keeps the same total.","","",""]}},"hints":["Add 1 to one addend and subtract 1 from the other."],"explanation":"50 + 25 keeps the same total."},{"content":"Which expression is equal to 63 − 19?<br>[[choice-8]]","widgets":{"choice-8":{"type":"choice","options":["64 − 20","63 − 20","62 − 20","64 − 19"],"answer":[0],"explanations":["Adding 1 to both numbers keeps the difference unchanged.","","",""]}},"hints":["Increase both numbers by 1."],"explanation":"Adding 1 to both numbers keeps the difference unchanged."}],"mix":1}